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Title: Grasses
       A Handbook for use in the Field and Laboratory

Author: H. Marshall Ward

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Language: English

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  CAMBRIDGE BIOLOGICAL SERIES.

  GENERAL EDITOR:--ARTHUR E. SHIPLEY, M.A., F.R.S.
  FELLOW AND TUTOR OF CHRIST’s COLLEGE, CAMBRIDGE.

  GRASSES.

  CAMBRIDGE UNIVERSITY PRESS WAREHOUSE,
  C. F. CLAY, MANAGER.
  London: FETTER LANE, E.C.
  Edinburgh: 100, PRINCES STREET.

  [Illustration]

  ALSO

  London: H. K. LEWIS, 136, GOWER STREET, W.C.
  Leipzig: F. A. BROCKHAUS.
  New York: G. P. PUTNAM’S SONS.
  Bombay and Calcutta: MACMILLAN & CO. LTD.

  [_All Rights reserved._]




  GRASSES

  A HANDBOOK FOR USE IN THE FIELD
  AND LABORATORY.

  BY

  H. MARSHALL WARD, SC.D., F.R.S.

  LATE PROFESSOR OF BOTANY IN THE UNIVERSITY OF CAMBRIDGE.


  CAMBRIDGE:
  AT THE UNIVERSITY PRESS.
  1908

  _First Edition 1901 Reprinted 1908_




PREFACE.


The following pages have been written in the hope that they may be
used in the field and in the laboratory with specimens of our ordinary
grasses in the hand. Most of the exercises involved demand exact
study by means of a good hand-lens, a mode of investigation far too
much neglected in modern teaching. The book is not intended to be a
complete manual of grasses, but to be an account of our common native
species, so arranged that the student may learn how to closely observe
and deal with the distinctive characters of these remarkable plants
when such problems as the botanical analysis of a meadow or pasture,
of hay, of weeds, or of “seed” grasses are presented, as well as when
investigating questions of more abstract scientific nature.

I have not hesitated, however, to introduce general statements on the
biology and physiological peculiarities of grasses where such may serve
the purpose of interesting the reader in the wider botanical bearings
of the subject, though several reasons may be urged against extending
this part of the theme in a book intended to be portable, and of direct
practical use to students in the field.

I have pleasure in expressing my thanks to Mr R. H. Biffen for
carefully testing the classification of “seeds” on pp. 135-174, and to
him and to Mr Shipley for kindly looking over the proofs; also to Mr
Lewton-Brain, who has tested the classification of leaf-sections put
forward on pp. 72-82, and prepared the drawings for Figs. 21-28.

That errors are entirely absent from such a work as this is perhaps too
much to expect: I hope they are few, and that readers will oblige me
with any corrections they may find necessary or advantageous for the
better working of the tables.

The list of the chief authorities referred to, which students who
desire to proceed further with the study of grasses should consult, is
given at the end.

I have pleasure in acknowledging my indebtedness to the following
works for illustrations which are inserted by permission of the
several publishers:--Stebler’s _Forage Plants_ (published by Nutt &
Co.), Nobbe’s _Handbuch der Samenkunde_ (Wiegandt, Hempel and Parey,
Berlin), Harz’s _Landwirthschaftliche Samenkunde_ (Paul Parey, Berlin),
Strasburger and Noll’s _Text-Book of Botany_ (Macmillan & Co.),
Figuier’s _Vegetable World_ (Cassell & Co.), Lubbock’s _Flowers, Fruits
and Seeds_ (Macmillan & Co.), Kerner’s _Natural History of Plants_
(Blackie & Son), and Oliver’s _First Book of Indian Botany_ (Macmillan
& Co.).

It is impossible to avoid the question of variation in work of this
kind, and students will without doubt come across instances--especially
in such genera as _Agropyrum_, _Festuca_, _Agrostis_ and _Bromus_--of
small variations which show how impossible it is to fit the facts
of living organisms into the rigid frames of classification. It
may possibly be urged that this invalidates all attempts at such
classifications: the same argument applies to all our systems, though
it is perhaps less disastrous to the best Natural Systems which attempt
to take in large groups of facts, than to artificial systems selected
for special purposes. Perhaps something useful may be learned by
showing more clearly where and how grasses vary, and I hope that the
application to them of these preliminary tests may elucidate more facts
as we proceed.

H. M. W.

CAMBRIDGE, _April_, 1901.




CONTENTS.


  CHAPTER I.
                                                              PAGE

  THE VEGETATIVE ORGANS                                          1


  CHAPTER II.

  THE VEGETATIVE ORGANS (_continued_)                           17


  CHAPTER III.

  GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS   39


  CHAPTER IV.

  ANATOMY AND HISTOLOGY                                         62


  CHAPTER V.

  GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS
    OF THE LEAF                                                 72


  CHAPTER VI.

  GRASSES IN FLOWER                                             83

  CHAPTER VII.

  GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND
    INFLORESCENCES                                              99


  CHAPTER VIII.

  THE FRUIT AND SEED                                           119


  CHAPTER IX.

  CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS)            135


  BIBLIOGRAPHY                                                 175


  INDEX, GLOSSARY AND LIST OF SYNONYMS                         177




CHAPTER I.

THE VEGETATIVE ORGANS.


That grasses are interesting and important plants is a fact recognised
by botanists all the world over, yet it would appear that people in
general can hardly have appreciated either their interest or their
importance seeing how few popular works have been published concerning
their structure and properties.

Apart from their almost universal distribution, and quite apart from
the fascinating interest attaching to those extraordinary tropical
giants, the Bamboos, West Indian Sugar-cane, the huge Reed-grasses of
Africa, the Pampas-grasses of South America; and from the utilitarian
value of the cereals--Maize, Rice, Wheat and other corn, &c.--everyone
must be struck by the significance of the enormous tracts of land
covered by grasses in all parts of the world, the Prairies of North
America and the Savannahs of the South, the Steppes of Russia and
Siberia, and the extensive tracts of meadow and pasture-land in Europe
being but a few examples.

Although in the actual number of species the Grass family is by no
means the largest in the vegetable kingdom, for there are far more
Composites or Orchids, the curious sign of success in the struggle for
existence comes out in grasses in that the number of _individuals_
far transcends those of any other group, and that they have taken
possession of all parts of the earth’s surface. Some species are
cosmopolitan--e.g. our common Reed, _Arundo Phragmites_; while
others--e.g. several of our native species of _Festuca_ and _Poa_--are
equally common in both hemispheres. On the whole the Tropics afford
most species and fewest individuals, and the temperate regions most
individuals.

Considering their multifarious uses as fodder and food, for brewing,
weaving, building and a thousand other purposes, it is perhaps not too
much to say that if every other species of plant were displaced by
grasses of all kinds--as many indeed gradually are--man would still be
able to supply his chief needs from them.

The profound significance of the grass-carpet of the earth, however,
comes out most clearly when we realise the enormous amounts of energy
daily stored up in the countless myriads of green blades as they fix
their carbon. By decomposing the carbon-dioxide of the air in their
chlorophyll apparatus by the action of the radiant energy of the sun,
they build up starches and sugars and other plant-substances, which are
then consumed and turned into flesh by our cattle and sheep and other
herbivorous animals, and so furnish us with food. The whole theory of
agriculture turns on this pivot, and the by no means small modicum of
truth in such sayings as “All flesh is grass,” and that the man who can
make two blades of grass grow where one grew before deserves well of
his country, obtains a larger significance when it is realised that the
only real gain of wealth is that represented by the storage of energy
from without which comes to us by the action of green leaves waving in
the sunshine.

The true Grasses, comprising the Natural Order Graminaceæ--also written
Gramineæ--are often popularly confounded with other herbs which possess
narrow green ribbon-like leaves, or even with plants of very different
aspects--e.g. Cotton-grass (_Eriophorum_) and other Sedges, and the
names Rib-grass (_Plantago_), Knot-grass (_Polygonum_), Scorpion-grass
(_Myosotis_) and Sea-grass (_Zostera_), as well as the general usage of
the word grass to signify all kinds of leguminous and other hay-plants
in agriculture, point to the wider use of the word in former times.
This has been explained by the use of the words _gaers_, _gres_,
_gyrs_, and grass in the old herbals to indicate any kind of small
herbage.

In view of the importance of our British grasses in agriculture, I
have here put together some results of observation and reading in the
hope that they may aid students in recognising easily our ordinary
agricultural and wild grasses. During several years of work in the
fields, principally directed at first to the study of the parasitic
fungi on grasses, and subsequently to that of the importance of grasses
in forestry and agriculture, and to the variations they exhibit, the
need of some guide to the identification of a grass at any time of
the year, whether in flower or not, forced itself on the attention,
and although a botanist naturally turns to a good Flora when he has
the grass in flower, as the best and quickest way of ascertaining
the species, it soon became evident that much may be done by the
study of the leaves and vegetative parts of most grasses. Indeed
some are recognisable at a glance by certain characters well known
to continental observers: in the case of others the matter is more
difficult, and perhaps with a few it is impossible to be certain of the
species from such characters only.

Nevertheless, while the best means for the determination of species
are always in the floral characters so well worked up in the Floras of
Hooker, Bentham and others, there is unquestionably much value in the
characters of the vegetative organs also, as the works of Jessen, Lund,
Stebler, Vesque and others abroad, and Sinclair, Parnell, Sowerby and
others in this country attest.

Almost the only plants confounded with true grasses by the ordinary
observer are the sedges and a few rushes. Apart from the very different
floral structures, there are two or three easily discoverable marks for
distinguishing all our grasses from other plants (Fig. 1). The first is
their leaves are arranged in _two rows_, alternately, up the stems; and
the second that their stems are circular or flattened in section, or if
of some other shape they are _never triangular_ and _solid_[1] (Figs.
6 and 7). Moreover the leaves are always of some elongated shape, and
without leaf-stalks[2], but pass below into a _sheath_, which runs
some way down the stem and is nearly always perceptibly split (Figs.
8-13). Further, the stems themselves are usually terete, and distinctly
hollow except at the swollen nodes, and only branch low down at the
surface of the ground or below it[3].

[Illustration: Fig. 1. A plant of Oat (_Avena_), an example of a
typical grass, showing tufted habit and loose paniculate inflorescence
(reduced). Figuier.]

All our native grasses are herbaceous, and none of them attain very
large dimensions. In the following lists I term those small which
average about 6-18 inches in the height of the tufts, whereas those
over 3 feet high may be termed large, the tufts being regarded as
in flower. The sizes cannot be given very accurately, and starved
specimens are frequently found dwarfed, but in most cases these
averages are not far wrong for the species freely growing as ordinarily
met with, and in some cases are useful. I have omitted the rare species
throughout, and in the annexed lists have added the popular names.


LARGE GRASSES.

(Over 3 feet.)

  _Milium effusum_ (Millet-grass).
  _Digraphis arundinacea_ (Reed-grass).
  _Aira cæspitosa_ (Tufted Hair-grass).
  _Arrhenatherum avenaceum_ (False Oat).
  _Elymus arenarius_ (Lyme-grass).
  _Bromus asper_ (Hairy Brome).
  _B. giganteus_ (Tall Brome).
  _Festuca elatior_ (Meadow Fescue).
  _F. sylvatica_ (Reed Fescue).
  _Glyceria aquatica_ (Reed Sweet-grass).
  _G. fluitans_ (Floating Sweet-grass).
  _Arundo Phragmites_ (Common Reed).


MEDIUM GRASSES.

(1-3 feet.)

  _Phleum pratense_ (Timothy).
  _Avena pratensis_ (Perennial Oat-grass).
  _Anthoxanthum odoratum_ (Sweet Vernal).
  _Alopecurus agrestis_ (Slender Foxtail).
  _A. pratensis_ (Meadow Foxtail).
  _Agrostis alba_ (Fiorin).
  _Psamma arenaria_ (Sea Mat-grass).
  _Avena flavescens_ (Yellow Oat-grass).
  _Holcus lanatus_ (Yorkshire Fog).
  _Hordeum sylvaticum_ (Wood Barley).
  _H. pratense_ (Meadow Barley).
  _Agropyrum repens_ (Couch-grass).
  _A. caninum_ (Fibrous Twitch).
  _Lolium italicum_ (Italian Rye-grass).
  _Brachypodium sylvaticum_ (Wood False-Brome).
  _B. pinnatum_ (Heath False-Brome).
  _Bromus erectus_ (Upright Brome).
  _B. sterilis_ (Barren Brome).
  _B. arvensis_ (Field Brome).
  _Festuca ovina_ (var. _rubra_, &c.). (Sheep’s Fescue).
  _F. elatior_ (var. _pratensis_). (Meadow Fescue.)
  _Dactylis glomerata_ (Cock’s-foot).
  _Cynosurus cristatus_ (Crested Dog’s-tail).
  _Poa pratensis_ (Meadow-grass).
  _P. trivialis_ (Rough stalked Meadow-grass).
  _P. nemoralis_ (Wood Poa).
  _Molinia cærulea_ (Flying Bent).
  _Melica nutans_ (Mountain Melick).
  _M. uniflora_ (Wood Melick).


SMALL GRASSES.

(6-18 inches.)

  _Phleum arenarium_ (Sand Cat’s-tail).
  _Alopecurus geniculatus_ (Marsh Foxtail).
  _Agrostis canina_ (Brown Bent).
  _Aira flexuosa_ (Wavy Hair-grass).
  _Aira canescens_ (Grey Hair-grass).
  _A. præcox_ (Early Hair-grass).
  _A. caryophyllea_ (Silvery Hair-grass).
  _Nardus stricta_ (Moor Mat-grass).
  _Hordeum murinum_ (Wall Barley).
  _H. maritimum_ (Sea Barley).
  _Lolium perenne_ (Rye-grass).
  _L. temulentum_ (Darnel).
  _Bromus arvensis_ (var. _mollis_). (Field Brome).
  _Festuca ovina_ (Sheep’s Fescue).
  _F. Myuros_ (Rat’s-tail Fescue).
  _Briza media_ (Quaking-grass).
  _Poa maritima_ (Sea Poa).
  _P. annua_ (Annual Meadow-grass).
  _P. compressa_ (Flattened Meadow-grass).
  _P. alpina_ (Alpine Poa).
  _P. bulbosa_ (Bulbous Poa).
  _Triodia decumbens_ (Heath-grass).
  _Kœleria cristata_ (Crested Kœleria).

The roots of our grasses are almost always thin and _fibrous_ and are
adventitious from the nodes, frequently forming radiating crowns round
the base and easily pulled up, and usually broken in the process;
but in the case of a few moor grasses--especially _Nardus_ (Fig. 2)
and _Molinia_--the roots are so tough and thick (_stringy_) as to
resist breakage very efficiently. In stoloniferous grasses a similar
difficulty of removal may be caused in a slighter degree by the
underground stems. In a few cases, e.g. _Alopecurus bulbosus_ (Fig. 3),
_Poa bulbosa_, _Phleum pratense_ and _P. Bœhmeri_, _Arrhenatherum
avenaceum_, and to a slighter extent in _Poa alpina_ and one or two
others, the lowermost internodes and sheaths of the stems may be
swollen and stored with food-materials, and a sort of _tuber_ or _bulb_
results; this is especially apt to occur in dry sandy soils. In old
lawns, pastures, &c., the roots of _Poa annua_ and others may have
nodules on them due to the presence of certain small Nematode worms,
_Heterodera_.

[Illustration: Fig. 2. _Nardus stricta._ Plant showing tufted habit,
and simple spikate inflorescence, with pointed spikelets all turned
towards one side (secund) on the rachis (reduced). Note also the
bristle-like (setaceous) leaves at length reflexed. Parnell.]

[Illustration: Fig. 3. _Alopecurus geniculatus_, var. _bulbosus_. Plant
(reduced) showing habit, bulbous shoots and cylindrical spike-like
inflorescences (Foxtail type). Notice the inflated sheaths, and the
“kneed” lower parts of the ascending stems. Parnell.]

Grasses are annual, biennial, or perennial, and it is often of
importance to know which. The point may usually be determined by
examining the shoots. If all the shoots have flowering stems in them,
and are evidently of the current year, the grass is an annual; but if
any shoots have leaves only, it is either biennial or perennial: to
determine which is not always easy, but in perennial grasses there
will generally be evident remains of older leaf-bases and shoots, and
if there are distinct underground stolons or creeping rhizomes as well
the point may be considered decided, and the grass is perennial, as
is the case with most of our important species. If all the shoots are
barren, the grass is a biennial in its first year of growth: if all
have flowering stems in them, but show traces of old leaf-bases of the
previous year, then the grass is a biennial in its second year. The
proof of biennial character is not always easy, however, and a few
grasses may be either annual or biennial, or biennial or perennial,
according to conditions--e.g. species of _Hordeum_, _Bromus_, &c. In
the following lists I have given the duration of the principal grasses,
where the character is especially important.


ANNUALS.

  _Phleum arenarium._
  _Aira præcox._
  _A. caryophyllea._
  _Hordeum murinum._
  _H. maritimum._
  _Lolium temulentum._
  _Festuca Myurus._
  _Briza minor._
  _Poa rigida._
  _P. annua._


ANNUALS

which may become biennial or perennial.

  _Alopecurus geniculatus._
  _Hordeum pratense._
  _Lolium perenne._
  _L. italicum_ (may be perennial).
  _Bromus asper_ (may be perennial).
  _B. sterilis._
  _B. arvensis_ (may be perennial).


PERENNIALS.

  _Holcus lanatus._
  _H. mollis._
  _Nardus._
  _Hordeum sylvaticum._
  _Agropyrum._
  _Brachypodium._
  _Bromus erectus._
  _B. giganteus._
  _Festuca ovina._
  _F. elatior._
  _F. sylvatica._
  _Dactylis._
  _Cynosurus cristatus._
  _Briza media._
  _Milium._
  _Anthoxanthum._
  _Digraphis._
  _Phleum pratense._
  _Alopecurus pratensis._
  _Agrostis alba._
  _A. canina._
  _Psamma._
  _Aira cæspitosa._
  _A. flexuosa._
  _A. canescens._
  _Avena pratensis._
  _A. flavescens._
  _Arrhenatherum._
  _Glyceria aquatica._
  _G. fluitans._
  _Poa maritima._
  _P. compressa._
  _P. pratensis._
  _P. trivialis._
  _P. nemoralis._
  _P. alpina._
  _P. bulbosa._
  _Molinia._
  _Melica._
  _Triodia._
  _Kœleria._
  _Arundo._

[Illustration: Fig. 4. _Catabrosa aquatica._ Plant showing the creeping
habit, rooting nodes, and paniculate inflorescence (reduced). Parnell.]

The rhizome of a perennial grass is continued sympodially by means of
buds branching from the lowermost joints of the flowering shoots, and
some importance is attached to the mode of spreading of these lateral
sprouting shoots. The buds always arise in the axils of the lower
leaf-sheaths--i.e. they are _intra-vaginal_. If they remain
intra-vaginal during further growth, the shoots are forced upwards and
only _tufts_ (Fig. 2) are formed, except in so far as such shoots may
fall prostrate on the surface of the ground later, and throw out roots
from their nodes, and so act as _runners_ or offsets, or put out a few
roots &c. as they ascend through the soil. But in many cases the buds
soon burst through the leaf-sheaths, and develope as _extra-vaginal_
shoots, and may then run horizontally as underground _stolons_.
Only creeping grasses of these latter kinds can rapidly cover large
areas[4]: the grasses with intra-vaginal shoots only can only make
tufts or “tussocks.” Several peculiarities in the habits of grasses
depend on these facts. The following are the most important creeping,
or _stoloniferous_ species, contrasted with the much more common
_tufted_ and the far rarer grasses with _runners_ above ground (Fig.
4). Some of these (_Elymus_, _Psamma_, &c.) are of great importance as
sand-binders.—


With intra-vaginal branches only.

  _Lolium_--slightly stoloniferous.
  _Festuca elatior_--slightly stoloniferous.
  _Avena flavescens_--slightly stoloniferous.
  _Phleum pratense_--no stolons, but may be bulbous.
  _Dactylis_--no stolons.
  _Festuca ovina_--no stolons.
  _Poa alpina_--no stolons.
  _Cynosurus_--no stolons.


With extra-vaginal shoots.

  _Arrhenatherum_--short stolons, sometimes bulbous.
  _Holcus lanatus_--creeping.
  _Alopecurus pratensis_--long stolons.
  _Anthoxanthum_--slightly stoloniferous.
  _Agrostis alba_ (var. _stolonifera_)--long stolons and runners.
  _Digraphis_--long stolons.
  _Poa pratensis_--long stolons.
  _P. trivialis_--runners only.
  _Festuca heterophylla_, Lam.--a variety of _F. ovina_ with slight
    stolons.
  _F. rubra_ (Linn.)--a variety of _F. ovina_ with long stolons.
  _Bromus erectus_--no stolons.
  _B. inermis_--long stolons.


Creeping below ground and truly stoloniferous.

  _Agropyrum._
  _Elymus._
  _Psamma._
  _Poa pratensis._
  _P. compressa._
  _Agrostis alba_ (var. _stolonifera_).
  _Alopecurus pratensis._
  _Brachypodium_ (slightly).
  _Bromus erectus_ (slightly).
  _Festuca ovina_ (var. _rubra_, Linn.).
  _F. elatior_ (slightly).
  _Briza_ (slightly).
  _Glyceria._
  _Poa maritima._
  _Melica._
  _Arundo._


Tufted Grasses.

  _Milium._
  _Agrostis alba_ (on downs, &c.).
  _Aira cæspitosa._
  _A. flexuosa._
  _A. canescens._
  _A. præcox._
  _A. caryophyllea._
  _Avena pratensis_ (slightly creeping).
  _Arrhenatherum._
  _Nardus_ (Fig. 2).
  _Hordeum sylvaticum._
  _Lolium._
  _Bromus._
  _Festuca ovina_ (except some varieties).
  _F. sylvatica._
  _F. Myurus._
  _Dactylis._
  _Cynosurus._
  _Poa rigida._
  _P. annua._
  _P. trivialis._
  _P. nemoralis._
  _P. alpina._
  _P. bulbosa._
  _Molinia._
  _Triodia._
  _Kœleria._


Creeping above ground (with runners).

  _Holcus lanatus._
  _Alopecurus geniculatus._
  _Agrostis alba_ (var. _stolonifera_).
  _Hordeum pratense_ (slightly).
  _H. murinum_ (slightly).
  _Catabrosa_ (Fig. 4).
  _Cynodon_ (Fig. 5).

Hackel has pointed out that a distinction must be drawn between the
true nodes of the _culm_, and the swellings often found at the base of
the _sheaths_ themselves over these: the latter are often conspicuous
when the former are inconspicuous--e.g. most species of _Agrostis_,
_Avena_, _Festuca_, &c.

The nodes are of importance in the description of a few species
only--e.g. they are usually dark coloured in certain _Poas_ such as _P.
compressa_ and _P. nemoralis_; they are sharply bent in _Alopecurus
geniculatus_, and may be so in other species if “layed” by wind, rank
growth, &c.

A point of considerable classificatory value is the shape of the
transverse section of the shoot, which is correlated with the mode of
folding up of the young leaf-blades.

[Illustration: Fig. 5. _Cynodon Dactylon._ Plant (reduced) showing
creeping and stoloniferous habit, and peculiar inflorescence of
digitate spikes. Parnell.]

In most grasses the blades are _convolute_--i.e. rolled up like the
paper of a cigarette, one edge over the other--and the section of
the shoot is round (Fig. 7). In some cases, however, the leaves are
_conduplicate_--i.e. each half of the lamina is folded flat on the
other, the upper sides being turned face to face inwards, with the
mid-rib as the hinge--and in this case the shoots are more or less
compressed (Fig. 6).

[Illustration: Fig. 6. _Dactylis glomerata._ Transverse section of a
leaf-shoot (× 5). _A_, conduplicate leaf-blade. _B_, sheath. Stebler.]

[Illustration: Fig. 7. _Digraphis arundinacea._ Transverse section of a
leaf-shoot (× 5). _A_, sheath. _B_, convolute leaves. Compare Fig. 14.
Stebler.]

In these latter cases the transverse section may be elliptical--e.g.
_Poa pratensis_ and _P. alpina_, _Briza_, &c., or more flattened
and linear-oblong--e.g. _Glyceria fluitans_--with the flattened
sides straight, or the section is oval but pointed more or less at
each end owing to projecting keels and leaf-edges, and the form is
_naviculate_--e.g. _Glyceria aquatica_, _Dactylis_ (Fig. 6)--or, the
sides being less flattened, more or less _rhomboidal_ as in _Poa
trivialis_. In _Melica_ the leaves are convolute and the shoot-section
_quadrangular_.


Flat, and usually sharp-edged shoots.

  _Dactylis glomerata_ (Fig. 6).
  _Poa trivialis_, _P. annua_, _P. pratensis_, _P. compressa_,
    _P. maritima_, and _P. alpina_.
  _Glyceria aquatica_ and _G. fluitans_.
  _Avena pubescens._
  _Lolium perenne._




CHAPTER II.

THE VEGETATIVE ORGANS (_continued_).


The leaves of all our grasses consist of the _blade_, which passes
directly into the _sheath_, without any petiole or leaf-stalk (Fig. 1).

The sheath is usually obviously _split_, and so rolled round the
internode that one edge overlaps the other, but in the following
grasses the sheath is either quite _entire_, or only slit a short way
down, the two edges being fused as it were for the greater part of its
length.

Sheath more or less entire.

  _Glyceria aquatica_ and _G. fluitans_.
  _Melica uniflora_ and _M. nutans_.
  _Dactylis glomerata._
  _Poa trivialis_ (Fig. 8), _P. pratensis_, _P. alpina_.
  _Sesleria cærulea._
  _Bromus_ (all the species).
  _Briza media_ and _B. minor_.

In some cases--e.g. _Arrhenatherum_, _Bromus asper_, and _Holcus
lanatus_--the sheath is marked with a more or less prominent ridge
down its back, due to the continuation of the _keel_ of the leaf. The
sheath may also be glabrous or hairy, and grooved or not.

A few grasses are so apt to develope characteristic colours in their
sheaths, especially below, that they may often be recognised in winter
by this peculiarity.


Sheaths coloured.

  _Lolium_--all red.
  _Holcus_--red with purple veins.
  _Festuca elatior_--red.
  _Cynosurus_--yellow.
  _Alopecurus pratensis_, and
  _A. agrestis_--violet-brown, &c.
  _Festuca ovina_, var. _rubra_--red.

[Illustration: Fig. 8. _Poa trivialis. A_, base of blade. _B_,
ligule. _C_, sheath. _D_, culm (× about 3).]

[Illustration: Fig. 9. _Alopecurus pratensis. A_, base of blade. _B_,
ligule. _C_, sheath. Slightly magnified.]

[Illustration: Fig. 10. _Avena flavescens._ Lettering as before (× 2).
Note the split sheath, the hairs and ridges. Stebler.]

At the junction of the blade with the sheath there is in most cases a
delicate membranous upgrowth of the former, more or less appressed to
the stem, and called the _Ligule_ (Figs. 8-13). Its use is probably
to facilitate the shedding of water which has run down the leaf; and
so lessen the danger of rotting between the sheath and stem: possibly
the shelves and ears commonly met with at the base of the lamina (Fig.
12) aid in the same process. This ligule may be long or short, acute
or obtuse, toothed or entire, or it may be reduced to a mere line, or
tuft of hairs, or even be obsolete, and is of considerable value in
classification--e.g. the ligule is obsolete or wanting in _Melica_,
_Festuca ovina_, _F. Myurus_, _F. elatior_, _Kœleria_ and _Panicum_.

It is represented by a tuft of hairs in _Molinia_, _Triodia_ and
_Arundo_.

[Illustration: Fig. 11. _Lolium perenne. A_, base of lamina, _B_,
ligule. _C_, sheath (× 3). Note the low ribs, and absence of hairs
(glabrous).]

[Illustration: Fig. 12. _Festuca elatior_, var. _pratensis_. _A_, base
of lamina. _B_, the extremely short ligule, with pointed ears. _C_,
sheath (× 3).]

[Illustration: Fig. 13. _Festuca ovina. A_, base of lamina. _B_,
ligular ears. _C_, sheath (× about 4). Stebler.]

Our other ordinary grasses have a more or less well-developed
_membranous_ ligule (Fig. 8).

The leaf-blade is long or short, broad or narrow, but always of some
elongated form such as linear, linear-lanceolate or linear-acuminate,
or subulate, setaceous, &c., varying as to the degree of acuteness of
the apex, and the tapering of the base.

In the following native grasses the _form_ of the lamina affords a
useful character.

The base tapers to the sheath below--i.e. the leaf is more or less
linear-lanceolate--in _Molinia_, _Brachypodium_, _Melica_, _Milium_,
_Kœleria_, and the very rare _Hierochloe_; less distinctly so
in _Bromus asper_ and species of _Hordeum_. The base is rounded in
_Arundo_. In the following cases the leaves are setaceous, due to the
very narrow blade remaining permanently folded or inrolled at its
edges, and usually being thickened and hardened also (Figs. 13 and 18).
The habitat of these moor-and heath-grasses suggests that these are no
doubt adaptations to prevent excessive evaporation by the exposure of
too large a surface--e.g. various species of _Aira_, _Festuca ovina_,
_F. Myurus_ and allies, _Nardus_, and several other species; whereas,
conversely, the thin flat leaves of shade-grasses facilitate exposure
to light and transpiration. In _Avena pratensis_ and _Agrostis canina_
some of the leaves are involute and subulate, and the thickened leaves
of _Poa maritima_ also are turned up at the edges, and are +U+-shaped
in cross-section.

As we shall see later the degree of inrolling of many grass leaves
varies with circumstances.

In most others the blades are either flat (Figs. 8-12), or more or
less conduplicate on the mid-rib. The latter case occurs, for example,
in grasses with flattened shoots, especially at the lower part of the
blade--e.g. _Lolium perenne_, _Dactylis_, _Glyceria_, and some species
of _Poa_, and the cross-section of the leaf below, just before it
enters the sheath, is +V+-shaped. In _Glyceria_ the leaf-bases may show
yellow or brownish triangles.

Further characters of the leaves are derived from their texture, apex,
margins, mid-ribs and venation, hairiness, and especially the presence
and characters of the longitudinal ridges which run along the upper or
lower surface in many cases.

The venation is parallel from base to apex in nearly all our grasses,
but such is not always the case--e.g. in the exotic _Panicum plicatum_
the mid-rib, which enters the leaf with several vascular bundles,
gives off strong and weak veins below, which first diverge and then
run in arches which converge upwards: this leaf is also remarkable in
being _plaited_ (plicate) in vernation. In _Arundo Donax_ also the
veins, though approximately parallel, do not all run to the apex of the
tapering leaf; the outer ones end above in the margins and are shorter
than the mid-rib.

As regards _texture_, the leaves of most grasses are thin and
herbaceous; but in some they are dry and harsh to the touch. They are
thin and dry in _Agropyrum caninum_, _Hordeum pratense_, _H. murinum_,
_Avena pratensis_, &c., very hard and leathery (_coriaceous_) in
_Psamma_, _Nardus_, species of _Festuca_, _Aira_, _Agropyrum junceum_,
_Elymus_, &c. In aquatic grasses like _Glyceria_, the leaf is almost
spongy owing to the large air-chambers developed in the tissues. These
are easily visible with a lens.

The _apex_ is in most cases slender and tapering--_acuminate_; but
in some it is merely brought to a point (_acute_) as in _Catabrosa_,
_Glyceria_ and several species of _Poa_ and _Avena_, &c., usually
flat, but somewhat hooded or curved up in some Poas. In cases where
the leaves are _setaceous_ or _subulate_, the apex is like a thin
tapering bristle, and even flatter leaves may be so inrolled at the
tips as to have the apex prolonged into a sharp needle-like _pungent_
or _spinescent_ point--e.g. _Hordeum pratense_, _Avena pratensis_ to
a slight extent, and pronounced in _Elymus_, &c. In _Sesleria_ the
apex is rounded with a short, sharp, prickle-like median projection
(_mucronate_).

The passage of blade into sheath has already been described, but
the base of the blade may have its margins projecting as horizontal
shelves, like a Byron collar, round the sides of the throat of
the sheath, sometimes tinged with yellow or pink--e.g. _Lolium_,
_Holcus_, _Bromus inermis_, _Hordeum_; the ends of these may project
as _auricles_ or ears--e.g. _Festuca elatior_, _Elymus_, _Agropyrum_,
_Anthoxanthum_, _Bromus asper_, _Hordeum_, &c. In _Festuca ovina_ the
ears are short, stiff, and erect (Fig. 13).

The margin may be perfectly even, as in most grasses, or it is more
or less _scabrid_ or _scaberulous_, as in _Aira cæspitosa_, _Poa
maritima_, _Festuca elatior_, _Avena pratensis_, _Agrostis_, _Milium_,
_Phleum_, _Briza_, the minute teeth (_serrulæ_) pointing up or down.

The surface may be bright green, or glaucous, harsh, hairy or glabrous,
and is not uncommonly also _scabrid_, like a file or emery-paper, and
sometimes only when rubbed in one direction up or down, owing to the
minute teeth being directed all one way. These teeth are developed on
the ridges.

All our ordinary grass leaves are parallel-veined, and the vascular
strands (the veins) can usually be seen on holding the leaf up to the
light. In most cases the tissue is raised over the veins, as ridges or
“ribs,” and according to the height of these ridges the thinner parts
between look like deep or shallow furrows (cf. Figs. 8-16 and Chapter
IV.). If the leaf is held up to the light the ridges appear _dark_ in
proportion to their opacity--i.e. height or thickness--and the furrows
_light_ in proportion to the thinness of the tissues there. If the
contrast is very great, as in _Aira cæspitosa_ (Fig. 23), the furrows
seem like transparent sharp lines, and when, as in _Poa_, which is
practically devoid of ridges, the difference of thickness is small they
appear merely as fine striæ. These characters must be determined on
the fresh leaves, however, because the contraction in drying draws the
ridges closer together and tends to obliterate the lines.

[Illustration: Fig. 14. _Digraphis arundinacea._ Transverse section of
mid-rib and half the leaf (× about 6).]

[Illustration: Fig. 15. _Holcus lanatus._ Transverse section of
leaf-blade (× 10).]

[Illustration: Fig. 16. _Cynosurus cristatus._ Transverse section of
the leaf-blade (× 20). Stebler.]

The ridges are almost always evident--_Catabrosa_, _Poa_, and _Avena_
furnishing the chief exceptions--and are nearly invariably on the
upper surface: they are below in _Melica_, however; and their
relative numbers, heights and breadths, section--acute, rounded, or
flattened--furnish valuable characters; as also does the coexistence or
absence of hairs, asperities, &c.

[Illustration: Fig. 17. Transverse section of the leaf of _Festuca
elatior_, var. _pratensis_ (× 12).]

[Illustration: Fig. 18. Ditto of the leaf of _F. ovina_ (× 15).]

[Illustration: Fig. 19. Ditto of the leaf of _F. ovina_, var. _rubra_
(× 35).]

[Illustration: Fig. 20. _Festuca ovina_, var. _rubra_. Transverse
section of the blade of an upper leaf (× 35). Stebler.]

A very interesting anatomical adaptation is met with in the leaves of
many grasses which grow in dry situations (xerophytes) such as on sandy
sea-shores, exposed mountains and so forth. When the air is moist, in
wet weather or in the dews, and the sun’s rays not too powerful, the
leaf is spread out with its upper surface flat or nearly so, but when
the scorching sun and dry air or winds prevail, the leaves fold or
roll up, with the upper sides apposed or overlapping inside the hollow
cylinder thus made.

In such leaves some of the upper epidermal cells, either next the
mid-rib (_Sesleria_ &c.) or between the other ribs (_Festuca_ &c.)
are large and very thin-walled, full of sap when distended, and so
placed that as they lose water by evaporation they contract, and
so draw together the two halves of the lamina (_Sesleria_) or each
ribbed segment (_Festuca_), thus causing the infolding or inrolling
(see Chapter IV). Not only from the structure and actions of these
motor-cells, but also from the fact that the stomata are on the upper
surfaces and thus protected, and that the lower surfaces which alone
are exposed to the drought are defended by hard and impenetrable
tissues, we must look upon these as adaptations to the xerophytic
conditions.


Leaves prominently ridged.

  _Elymus._
  _Psamma._
  _Aira cæspitosa._
  _Lolium._
  _Cynosurus_ (Fig. 16).
  _Agrostis._
  _Alopecurus._
  _Glyceria fluitans._
  _Kœleria._
  _Festuca elatior._
  _Festuca Myurus_ (var. _sciuroides_).
  _Melica_ has ridges on the _lower_ surface.

Ridges are less prominent in _Phleum pratense_, _Briza_, _Agropyrum_,
_Triodia_, _Arrhenatherum avenaceum_.


Leaves practically devoid of ridges.

  _Poa_--all common species.
  _Glyceria aquatica._
  _Catabrosa aquatica._
  _Avena pratensis._

In some grasses the tissue over the mid-rib is considerably raised and
strengthened on the dorsal side of the blade as a “keel.”


Keel more or less prominent.

  _Arrhenatherum_ (sheath keeled).
  _Poa_ (all except _P. maritima_).
  _Dactylis._
  _Bromus._
  _Bromus asper_ (sheath keeled, often a white line).
  _Holcus lanatus_ (slight and decurrent) (Fig. 15).
  _Digraphis_ (Fig. 14).
  _Glyceria._

Most grasses are glabrous, but there are a number in which hairs are
nearly always a prominent feature. It must be remarked, however, that
with grasses, as with other plants, the character of pubescence is apt
to vary with the situation. In general it may be stated that a hairy
grass tends to become more glabrous in a moist situation, and more
pubescent in a dry one, but the rule is by no means absolute. In some
cases,--e.g. _Avena pubescens_, _A. flavescens_, _Agropyrum_, the hairs
are almost entirely confined to the crests of the ridges (Figs. 10,
15). The following is a list of hairy grasses.


HAIRY GRASSES.

  _Holcus_ (Fig. 15).
  _Molinia cærulea._
  _Brachypodium sylvaticum._
  _Agropyrum_ (variable).
  _Bromus asper._
  _B. mollis._
  _Hordeum._
  _Anthoxanthum._
  _Avena flavescens_ (Fig. 10).
  _A. pubescens._
  _Triodia._
  _Kœleria._


To a less extent.

  _Festuca sciuroides_ (on ribs).
  _Melica._

Grasses as a rule are devoid of strong scents[5] or tastes, but
_Anthoxanthum_ has a faint but distinct sweet odour, especially as
it dries--it is one of the grasses which give the scent to new-mown
hay--and a bitter flavour, and _Milium_, _Hierochloe_ and _Holcus_ are
also more or less bitter. _Spartina stricta_ emits a strong unpleasant
odour.

The habitat of grasses is of great importance as an aid to
determination. No one would expect to find a sea-shore grass growing in
a beech-forest, or an aquatic grass on a dry chalk-down; but they are
even more true to their habitats than this, and I append the following
lists of habitats of British grasses as of use in determining them,
though it is not pretended that the limits are absolute.

In the following list “pasture-grass” (P) means useful for grazing, and
“meadow-grass” (M) one that is especially valuable for mowing--i.e. for
hay. A “weed” (W) is used in its agricultural sense for a grass not
useful and not wanted on cultivated land, though often found there.


MEADOW-AND PASTURE-GRASSES.

  (P and M) _Dactylis glomerata_ (fields, &c.).
  (P and M) _Poa trivialis_ (meadow and pasture).
  (W) _Bromus arvensis_ (cultivated and waste places, meadow and pasture).
  (W) _B. sterilis_ (ruderal).
  (P and M) _Poa pratensis_ (meadow and pasture).
  (W) _Briza media_ (meadow and pasture).
  (P) _Avena pratensis_ (meadow and pasture, especially hilly).
  (P) _A. pubescens_ (var.)--dry.
  (P and M) _Lolium perenne_ (meadow, pasture and waste places).
  (P and M) _L. italicum_ (valuable culture grass).
  (P) _Cynosurus cristatus_ (downs).
  (M and P) _Festuca elatior_ (meadow and moist pasture, banks and
              river-sides).
  (W) _Agrostis alba and A. canina_ (pasture and waste places,
        wet or dry).
  (P and M) _Alopecurus pratensis_ (meadow and pasture).
  (W) _A. geniculatus_ (moist meadows and marshes).
  (P and M) _Phleum pratense_ (meadow and pasture).
  (P) _Arrhenatherum avenaceum_ (meadow, hedges and copse).
  (P and M) _Anthoxanthum odoratum_ (fields generally).
  (W) _Hordeum pratense_ (moist meadow and pasture).
  (W) _Holcus lanatus and H. mollis_ (meadow, pasture and waste).
  (P and M) _Avena flavescens_ (dry meadow and pasture).
  (W) _Avena fatua_ (corn-weed).
  (P) _Festuca ovina_ (light limestone pastures and chalk downs).


SHADE-GRASSES.

  Found in woods, copses, &c., under shade.

  _Melica uniflora_ (woods, &c.).
  _Bromus asper_ (hedges, thickets, and edges of woods).
  _B. giganteus_ (hedges and woods).
  _Aira cæspitosa_ (moist shade and damp hedges).
  _Poa nemoralis_ (woods, shady places and damp mountain rocks).
  _Milium effusum_ (moist woods, &c.).
  _Agropyrum caninum_ (woods and shady places).
  _Hordeum sylvaticum_ (woods and copse).
  _Brachypodium sylvaticum_ (woods, hedges and thickets).
  _Arrhenatherum avenaceum_ (meadows, hedges and copse).
  _Festuca sylvatica_ (mountain woods).


AQUATIC AND SEMI-AQUATIC GRASSES.

Found in wet ditches, ponds, and on marshes, river-banks, &c.

  _Glyceria fluitans_ (wet ditches and slow waters).
  _G. aquatica_ (wet ditches and shallow waters).
  _Alopecurus geniculatus_ (moist meadow and marsh lands).
  _Digraphis arundinacea_ (river-banks, marshes).
  _Arundo Phragmites_ (wet ditches, marshes and shallow waters).
  _Molinia cærulea_ (wet heaths and moors, woods and waste places).
  _Triodia decumbens_, _Agrostis alba_, _Catabrosa_ and _Calamagrostis_.


MOOR-AND HEATH-GRASSES.

Downs and dry hill-pastures.

  _Nardus stricta_ (moors, heaths and hilly pastures).
  _Aira flexuosa_ (heaths and hill pastures).
  _Molinia cærulea_ (wet heathy moors, woods and waste places).
  _Kœleria cristata_ (dry pasture).
  _Triodia decumbens_ (dry heathy and hilly pastures).
  _Festuca ovina_ (hilly pastures--especially dry and open--rarer
    in moist situations).
  _Agrostis vulgaris_ and _A. canina._


MARITIME OR SEASIDE GRASSES.

  _Poa maritima_ (maritime).
  _P. distans_ (sandy pastures and wastes near sea).
  _Elymus arenarius_ (coasts).
  _Psamma arenaria_ (coasts).
  _Poa bulbosa_ (waste places in S.E. of England).
  _Agropyrum junceum_ (coasts).
  _Hordeum maritimum_ (S. and E. coast).
  _Phleum arenarium_ (coasts).


RUDERAL OR VAGABOND GRASSES.

  Waste places, walls, road-sides and dry sandy situations.

  _Molinia cærulea_ (wet, heathy moors, woods and waste places).
  _Festuca Myurus_ (waste places, walls, road-sides).
  _F. ovina_ (hilly pastures and especially dry, rarely moist situations).
  _Aira caryophyllea_ (sandy and hilly pastures).
  _Aira præcox_ (sandy and hilly pastures).
  _Poa distans_ (sandy wastes near the sea).
  _P. compressa_ (dry, barren, waste ground).
  _P. annua_ (cultivated and waste lands and fields).
  _Agropyrum repens_ (fields and waste places).
  _Hordeum murinum_ (waste places and road-sides).
  _Holcus lanatus_ (meadow, pasture, and waste lands).
  _H. mollis_ (same--rarer).
  _Alopecurus agrestis_ (waste lands and roads in S. of England).
  _Lolium perenne_ (meadows, pastures and waste places).
  _L. temulentum_ (fields and waste places, not common).
  _Bromus sterilis_ (on way-sides, &c.).
  _B. arvensis_ (cultivated and waste meadows and pastures).
  _Poa rigida_ (dry, rocky places).

It is also often useful to know whether a grass is rare or local,
especially for the purpose we have in view, and I have therefore drawn
up the following list of rare, local or introduced foreign grasses
either not noticed at all, or only referred to incidentally in this
work.

In many cases these introduced foreign grasses have sprung up from
seeds brought over in cargoes of hay, wool, and other products and
packing materials, which in part accounts for their occurrence only
near certain sea-ports, manufacturing towns and so forth. Such
plants are frequently termed ballast plants. Foreign plants are also
introduced in seed, as mixtures or impurities, and frequently escape
from corn-fields &c.

  _Leersia oryzoides_ (ditches of Hants., Sussex and Surrey).
  _Panicum sanguinale_ (S. England).
  _P. verticillatum_ (fields in S. and E.).
  _P. glaucum_ (rarely introduced).
  _Hierochloe borealis_ (Thurso only).
  _Phleum alpinum_ (Highlands only).
  _P. Bœhmeri_ (Eastern counties, rare).
  _P. asperum_     ”       ”       ”
  _Phalaris canariensis_ (rare weed).
  _Alopecurus alpinus_ (Highlands).
  _Mibora verna_ (Anglesea and Channel Islands).
  _Lagurus ovatus_ (Suffolk coasts).
  _Polypogon monspeliensis_ (rare, in S. England near sea).
  _P. littoralis_ (salt marshes S. England).
  _Agrostis setacea_ (dry heaths of S. Wales).
  _A. Spica-venti_ (sandy fields of E. counties).
  _Gastridium lendigerum_ (fields and waste places in S. Wales
    and Norfolk).
  _Calamagrostis Epigeios_ (moist glades &c. in Scotland).
  _C. lanceolata_ (moist shades, scattered in England).
  _C. stricta_ (bogs, &c., very rare).
  _Cynodon Dactylon_ (waste and cultivated lands near sea in Scotland).
  _Spartina stricta_ (salt marshes S. and E. coast).
  _Lepturus incurvatus_ (scattered on shores).
  _Bromus maximus_ (Jersey).
  _B. madritensis_ (roads and waste, Scotland and Tipperary).
  _B. inermis_ (introduced from Hungary).
  _Lolium italicum_ (introduced from Lombardy).
  _Festuca uniglumis_ (Irish and S.E. coast).
  _Poa procumbens_ (waste ground near sea).
  _P. loliacea_ (sandy sea-shores).
  _P. laxa_ (Ben Nevis, &c.).
  _P. alpina_ (Highlands and N.).
  _Catabrosa aquatica_ (shallow pools and ditches, scattered).

Finally, a few words may be said on a subject still in its
infancy--that of Indicator-plants. In many cases certain plants are
found so confined to certain classes of soil, that foresters and
agriculturists have claimed to be able to infer from their presence
the presence or absence of certain chemical or other constituents of
soils: on the contrary we find other plants so universally distributed
without reference to the quality of the soil, that they are not
indicative. The latter are often termed _ruderal_ or _vagabonds_ (see
p. 29). Without attempting too rigid a classification of Grasses in
this connection--which would be premature in this early state of our
knowledge--the following remarks are at least generally true.

A few grasses are Indicators of chalk and limestone--e.g. _Briza
media_, _Kœleria cristata_, and the exotic species _Stipa pennata_
and _Melica ciliata_.

The following are said to indicate a sufficiency of potassium salts,


In moister soils.

  _Digraphis arundinacea._
  _Phleum pratense._
  _Avena pubescens._
  _Arundo Phragmites._
  _Molinia cærulea._
  _Glyceria fluitans._


In drier soils.

  _Anthoxanthum odoratum._
  _Alopecurus pratensis._
  _Agrostis alba._
  __Holcus lanatus.__
  _Arrhenatherum._
  _Kœleria cristata._
  _Briza media._
  _Dactylis glomerata._
  _Cynosurus cristatus._
  _Poa pratensis._
  _P. trivialis._
  _P. compressa._
  _Festuca elatior._
  _Lolium perenne._

Grasses like _Bromus arvensis_ indicate the existence of clay in the
soil.

While the following are indicative of sand,

  _Aira caryophyllea._
  _A. præcox._
  _A. canescens._
  _Festuca ovina._
  _Bromus sterilis._

And only if the sandy soil is moist and of better quality, owing to a
certain proportion of humus, the following,

  _Anthoxanthum odoratum._
  _Agrostis alba._
  _Dactylis glomerata._
  _Arrhenatherum avenaceum._
  _Avena pubescens._
  _Poa pratensis._

That the soil contains considerable quantities of common salt--sodium
chloride--may be inferred if the following grasses occur,

  _Psamma arenaria._
  _Elymus arenarius._
  _Hordeum maritimum._
  _Agropyrum junceum_, &c.

The existence of much humus is indicated by such shade grasses as

  _Melica uniflora._
  _M. nutans._
  _Milium effusum._
  _Bromus giganteus._
  _B. asper._
  _Brachypodium sylvaticum._

Whereas soils known as “sour,” though containing much vegetable
remains, may be suspected if the following grasses abound on them,

  _Aira cæspitosa._
  _Nardus stricta._
  _Alopecurus geniculatus._
  _Molinia cærulea_;

especially if sedges and rushes coexist with them.

When cuttings are made in forests, such grasses as the following are
very apt to appear, and may do harm to young plants,

  _Festuca ovina_ and varieties.
  _Agrostis alba._
  _Holcus mollis._
  _Aira flexuosa_, &c.

The grasses more especially indicative of particular classes of
forest-soils are chiefly the wood-species (see p. 28), and need not be
further specified. In gaps, borders, and copses--half-shade--we find
several common grasses--e.g.

  _Anthoxanthum odoratum._
  _Agrostis alba._
  _Aira flexuosa._
  _Holcus lanatus._
  _Arrhenatherum avenaceum._
  _Triodia decumbens._
  _Dactylis glomerata._
  _Festuca rubra._
  _Brachypodium pinnatum._
  _Hordeum sylvaticum._

Whereas

  _Poa nemoralis_,
  _Festuca sylvatica_,
  _Agropyrum caninum_,
  _Melica_,
  _Milium_,
  _Bromus asper_,
  _B. giganteus_,
  _Brachypodium sylvaticum_,

are more likely to be met with in the deep shade inside the forest.

On the other hand there are vagabond grasses which seem to show no
signs of preference for one soil over another--e.g. _Poa annua_--though
in some cases these _ruderal_ plants indicate the presence of rotting
substances, on ash-heaps and rubbish of various kinds.

With reference to the above, however, the student must not forget
that very complex relations are concerned in changes of soil, shade,
moisture, elevation, &c. and that although experienced observers can
draw conclusions of some value from the presence of _numerous species
and individuals_ on a given soil, no one must conclude too readily that
a soil is so and so, from observing solely that a particular kind of
grass will grow there.

An excellent example of what may be done by applying such knowledge
as exists of the habits of grasses, is afforded by the historic case
of the planting up of shifting sand-dunes with species like _Psamma
arenaria_, _Elymus arenarius_, _Agropyrum junceum_, &c. (together
with sand-binding species of sedges) and so not only fixing the sand,
but preparing it for gradual afforestation with bushes and eventually
trees, and so saving enormous tracts of land and sums of money, as has
been done on the West coasts of France.

Moreover, the action of ruderal plants--including grasses--is to
completely alter the nature of the poor soil and gradually fit it for
other plants. Coverings of grass greatly affect the actions of heat and
sunshine on the surface soil, and modify the effects of radiation and
evaporation, to say nothing of the penetrating and other effects of the
roots.

Rhizomes and stolons break up stiff soils; and every engineer
and forester knows how useful certain grasses are in keeping the
surface-soil from being washed down by heavy rains on steep hill-sides
or embankments.

On the other hand, luxuriant growths of tall grasses may do harm to
young plants, by their action as weeds and especially as shade-plants;
though foresters can employ them in the latter capacity, under
restrictions, to shelter young trees from the sun. Again, too much dry
grass near a forest offers dangers from fire; and it is a well known
fact that certain injurious animals, e.g. mice and other vermin, are
favoured by a covering of grass.

Graminaceæ are for the most part chalk-fleeing plants, in spite of the
fact that certain species can grow in very thin layers of soil on chalk
downs. They must be regarded as requiring moderate supplies of humus as
a rule, and even sand-loving grasses are not real exceptions.

The physiognomy of the grasses has always been regarded as a striking
one, and Humboldt classed it as one of his 19 types of vegetation.
As is well known they are sociable plants, often covering enormous
areas--prairies, alps, steppes, &c.--with a few species, alone or
densely scattered throughout a mixed herbage. They also represent
characteristically the sun-plants, the erect leaves exposing their
surfaces obliquely to the solar rays, and being often folded and nearly
always narrow.

The dead remains of these sociable grasses are an important factor in
protecting the soil against drought and in facilitating humification,
as well as in covering up plants during long winters or dry seasons,
keeping the ground warmer and moister, and generally lessening the
effect of extremes.

Many Graminaceæ are pronounced xerophytes, the epidermis often being
developed as a water-storing tissue, while the erect leaves roll
themselves in intense light, the stomata being situated accordingly.
The halophytic strand-plants _Psamma arenaria_, _Elymus arenarius_,
_Agropyrum junceum_, and other Dune-species, as well as species of
_Aira_, _Festuca_, _Anthoxanthum_, _Stipa_, _Lygeum_, _Aristida_,
&c. are examples. The heath-grasses--e.g. _Festuca ovina_, _Nardus
stricta_, _Molinia cærulea_--also come under this category.

Many of the strand-plants (halophytes) _Agropyrum_, _Psamma_, _Elymus_,
are covered with waxy bloom, and have long rhizomes which bind the sand
and form new soil, a property largely taken advantage of in certain
forest operations.

Other grasses, particularly annual species, show their adaptation to
xerophytic habits by forming bulbous store-houses at the base of the
culms--e.g. _Phleum arenarium_.

Some Graminaceæ are hydrophytes, such as _Arundo_, _Glyceria_,
&c., with large intercellular spaces in their tissues; while
many species--e.g. _Aira cæspitosa_, _Agrostis canina_, _Molinia
cærulea_--grow on wet moor-lands, forming perennial tufts, with or
without creeping rhizomes.

The mesophyte grasses are especially characteristic of what may be
termed carpets--a lawn is a good example on a small scale, though of
course we must remember that here the struggle for existence has been
artificially interfered with more or less. Such carpets consist of the
densely interwoven rootlets and rhizomes forming sod, and contain much
humus from the accumulated débris of former years. These grass-carpets
may be composed of nearly pure growths of a few species, or of very
many different grasses and other herbage. They are common in Arctic
regions, on Alps, and in temperate climates generally, where we know
them as meadows, hay-fields, pasture and lawns.

The Bamboos in the wider sense have a physiognomy of their own, e.g. in
India, and may drive out most other plants and form dense undergrowths
or jungle of interlaced stems and leaves and thorny shoots. Similar
growths occur on the Andes and elsewhere in South America. In some
parts of India and tropical Asia the taller bamboos form aggregates
comparable to dense forests, and such forests are common on the
banks of several large tropical rivers. Most of these Bamboos are
xerophytes. Bamboos are neither confined to the tropics, nor to
warmer regions, however, for species are known from distinctly cool
regions--e.g. South America--or even from near the snow line--e.g.
Chili, the Himalayas, Japan, &c., and the number of species known as
hardy is increasing annually, as is evident on examining our larger
English gardens.

The permanence and character of extensive grasslands, especially
prairies, savannahs, and steppes, are much affected by the periodical
firing they are exposed to in the dry season, and large tracts of
country in various parts of the world would doubtless bear forests or
other vegetation if not thus fired, while in other cases the herbage
would be differently constituted were firing discontinued.

The following chapter embodies an attempt to classify our British
grasses solely for purposes of identification when not in flower. It
is not claimed that the arrangement is the best possible, nor that it
is complete, and I need hardly say that corrections will be gratefully
received.




CHAPTER III.

GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS.


I. SHEATHS ENTIRE EXCEPT WHERE THOSE OF LOWER LEAVES ARE BURST BY
BRANCHES, &C.

  +A. Aquatics with the sheaths reticulated, owing to large
      air-cavities. Leaves equitant, linear acute, often
      floating.+

_Glyceria fluitans_ (Br.). Floating sweet grass. Somewhat coarse, but
useful pasture in water-meadows and fens. Sweet-tasting.

Section of sheathed leaves linear oblong; sheath striate or furrowed,
keeled; leaf ribbed; ligule broad acute. Leaf-base with a yellow
triangle. Smooth.

_Glyceria aquatica_ (Sm.). Reed sweet grass. Especially given to
growing in the water-courses and on banks instead of spreading in the
water-meadows, &c. Sweet-tasting.

Section of sheathed leaves broadly naviculate; sheath smooth, no keel;
leaf not ribbed, thick and inflated with large air-cavities; ligule
short. Leaf-base with a brown triangle. Margins and keel rather rough.

  These two species of _Glyceria_ are distinguished by their
  shoot-sections and the ridges of the leaves of _G. fluitans_: they
  often occur in the same ditch.

  They cannot readily be confused with others on account of their
  aquatic habit, and the characters given. The only other aquatic
  or semi-aquatic species are forms of _Catabrosa_, _Digraphis_,
  _Arundo_, _Alopecurus geniculatus_, _Molinia cærulea_ and the rare
  _Calamagrostis_.

  The ligule and flat shoots with closed sheaths alone suffice to
  distinguish it from the round and split sheathed _Arundo Phragmites_;
  and the round shoots of _Digraphis_, its split sheath and firm
  leaves, suffice to distinguish it.

  _Molinia_ also has a tuft of hairs instead of a ligule, and a split
  sheath, and its habit is different.

  _Alopecurus geniculatus_, with its “kneed” shoots, has a totally
  different habit from _Glyceria_, and its very high ridges and want of
  visible air-chambers complete the diagnosis.

  _Catabrosa_ is a small creeping aquatic with very flaccid leaves,
  quite glabrous and soft. Also sweet-tasting.

  +B. Not aquatic, and devoid of visible air-chambers in leaf or
      sheath. Often perennial, i.e. having stolons or other branches
      with no rudiments of flowers in them, and with relics of old
      leaf-bases.+

    (α) Sections of sheathed leaves acute: either two-edged or
        four-edged.

      (1) Section of sheathed leaves quadrangular. Blades of leaf thin
          and dry, sparsely hairy. Sheath quite entire. Woods and shady
          places.

_Melica uniflora_, L. (Wood Melick). Lamina slightly tapered below,
convolute. Ligule obsolete, with a stiff subulate process on the sheath
opposite the blade-insertion. Ridges below, but not above.

_Melica nutans_, L. (Mountain Melick). Ligule longer, and without the
awl-shaped peg. Only in Scotland and W. of England.

  Both are shade grasses of no agricultural value.

  _M. uniflora_, with its quadrangular shoots and anti-ligular peg,
  cannot be confounded with any other grass.

      (2) Sections of sheathed leaves more or less acutely two-edged,
          owing to the keels of the compressed equitant leaves.

        (i) _Shoots broad and fan-like, much compressed, with old
            brown leaf-sheaths below, sometimes burst by the
            intra-vaginal branches: leaf ridgeless, with prominent
            keel. No underground stolons._

_Dactylis glomerata_, L. (Cock’s-foot). An early and quick-growing
pasture-grass, which forms much aftermath. Grows on all soils. Often
coarse. Coarse tussocks, and harsh, with broad thick succulent
bluish-green leaves.

Section of sheathed leaves acutely naviculate. Prominent obtuse ligule,
torn above. Lamina long, rough, acute, with white lines if held up, and
serrulate edges. No flanking lines[6]. No stolons (Fig. 6).

  There is a cultivated variety of _Dactylis_ with broad opaque
  white stripes down the leaves: these are totally different
  from the translucent white stripes seen on holding the wild
  form, or _Aira cæspitosa_, up to the light. Another cultivated
  “ribbon-grass”--_Digraphis_--has _round_ shoots, _split_ sheaths, and
  a different habit, and the same applies to its wild form.

  Probably the only serious chances of confusion with _Dactylis_ are
  between it and _Poa pratensis_, which also has flattened shoots
  and closed sheath; but in the latter the section of the shoot is
  _elliptical_--not _naviculate_,--the keel is far less prominent, and
  the ligule shorter. Moreover _P. pratensis_ is a creeping
  stoloniferous grass, less harsh, and with less pointed leaves.

  The distance to which the sheath is torn may be from 1/8 to 1/2 down.
  Leaves tend to remain conduplicate. Margins serrulate with teeth
  extremely short and directed forwards.

        (ii) _Shoots compressed but narrow: the section almost
            rhomboid with rounded edges._

_Poa trivialis_, L. (Rough-stalked Meadow-grass). Conspicuous in deep
rich pastures and orchards, preferring slight shade and rich soil.
Valuable pasture and hay grass.

Rootstock shortly creeping, branches extra-vaginal and above ground,
shoots rough. Blade narrow, harsh, with an acute point, thin, shining
below, ridgeless, with flanking lines and keel. Ligule acute, and short
or long (Fig. 8).

_Sesleria cærulea_, Ard. (Blue Moor-grass), of our northern limestone
hills, has narrow, flat, glaucous blue, stiff, mucronate leaves, with
scabrid apex. Ligule ciliate.

  _Poa trivialis_ is most likely to be confounded with other Poas,
  especially _P. annua_ and _P. pratensis_, since they both have thin
  leaves and flat shoots; but _P. annua_ has a split sheath, less acute
  and duller leaves, is annual, and less harsh, and the shoot-section is
  flatter at the sides and rounder at the ends.

  _Poa pratensis_, L. is larger and more stoloniferous, with both
  extra- and intra-vaginal branches, culms erect and smooth, sheaths
  smooth, and the shoot-sections elliptical--not cornered or
  rhomboidal--and with darker green and larger, thicker, 7-veined,
  more glossy, and less harsh leaves, with shorter, blunter ligule.

  _Poa compressa_, L. also presents difficulties, but the sheath is
  split, and the ligule is shorter than in _P. trivialis_, the leaves
  thicker, and the shoot-sections more linear-oblong or elliptical.


    (β) Sections of sheathed leaves rounded, circular or oval,
        there being no prominent keels.

      (1) Section of sheathed leaves circular or nearly so, the shoots
          being only slightly compressed.

        * _Perennial._

_Bromus inermis_ (Awnless Brome).

Sections circular, the leaves being convolute, base shelving. Glabrous
sheaths and leaves. Stoloniferous. Ligule short, truncate, and finely
toothed. A forage grass of the Hungarian steppes. Now being grown in
this country, but of doubtful value here.

_Bromus erectus_, Huds. (Upright Brome). A weed.

Sections oval and rounded, but leaves equitant. Radical leaves remain
folded and almost subulate, hairy edges. No stolons. Fields, &c. It is
a weed on dry lands, and of little or no value.

_Bromus asper_, Murr. (Hairy Brome). In thickets, &c.: a weed, and
useless. Leaves green, long, flat, hanging, and eared. Sheath with
scattered deflexed hairs. Lamina tapering at the base. Keel a white
line, ridges inconspicuous: distance between veins 2-3 times breadth of
latter. Ligule very short, toothed.

_B. giganteus_, L. (Tall Brome), also comes here. It is less common and
glabrous. Woods, &c., a useless weed.

        ** _Annual or biennial._

_Bromus mollis_ (_B. arvensis_, var. _mollis_, L.), Field Brome. A
too abundant and useless weed in water-meadows and hay-fields. Softly
downy. Blades very thin and not eared: dry.

_Bromus sterilis_, L. (Barren Brome). A useless weed. Rough and downy,
but less so than the last. Moist waysides, &c.

  The Bromes are extremely variable and difficult to determine by the
  leaves. The annual species are apt to be biennial or (_B. sterilis_)
  perennial; and some vary much as regards hairiness--e.g. _B. mollis_
  is connected by a series of semi-glabrous forms to varieties quite
  smooth, all grouped by Bentham under _B. arvensis_.

  _Bromus asper_, being auriculate and a shade-species, runs some risk
  of confusion with _Hordeum sylvaticum_, but _Hordeum_ has a _split_
  sheath and in _B. asper_ the translucent interspace between the
  ridges is 2-3 times as broad as in _Hordeum sylvaticum_.

  The other species of _Bromus_ are not eared, and their entire sheaths
  at once distinguish them from _Hordeum_.

  _Bromus giganteus_ has leaves glabrous and very like _Festuca
  elatior_. The red split sheaths of the latter, its sharp ears and
  prominent ridges afford the best distinctions; and _B. giganteus_ has
  broader leaves and more evident serrulation or descending bristles at
  the basal margins.

      (2) Section of sheathed leaves elliptical, owing to the shoots
          being compressed. Sheaths often only slightly split above.
          No hair on surface of leaves or sheaths.

        ✲ _Margins of leaves smooth and even. Blades without ridges,
           a keel and flanking lines, acute, base rounded. Ligule of
           lower leaves very short._

_Poa pratensis_, L. (Smooth-stalked Meadow-grass). An early and
valuable dry pasture-grass, but though deep-rooted, it yields thin
hay: its chief value is for “bottom grass” and in lawn mixtures, &c.
Leaves stiff and pointed. Extra-vaginal rooting underground stolons,
and intra-vaginal branches. Shoots smooth. Keel slight: seven principal
veins and smaller ones between. Leaves blunter and broader than in _P.
trivialis_.

_Poa alpina_, L. (Alpine Poa). On mountains in the north. No stolons.
4-5 veins on each side of the median one.

  _Poa pratensis_ presents similar difficulties to _P. trivialis_: for
  diagnoses see p. 42. It is distinguished from _P. nemoralis_ by its
  closed sheath, thicker, blunter and harder leaves, linear-elliptical
  shoot-sections, and light coloured nodes, as well as by its habit.
  All other Poas have shallow and poorly developed roots.

  _P. fertilis_ is a form very like _P. nemoralis_, with rougher leaves
  and longer ligule, introduced into cultivation.

        ✲✲ _Margins of leaves scaberulous with descending hairs.
             Very low flat ridges. Sheath smooth._

_Briza media_, L. (Quaking Grass). A weed in meadows, indicating poor
soil--e.g. moor-lands and chalk--but eaten by sheep. Tufted and slightly
creeping perennial. Ligules very short, entire.

_Briza minor_, L. (Lesser Quaking-grass). Annual. Leaves broader and
shorter, and ligules longer. In the south and rarer.


II. SHEATHS SPLIT, AT LEAST SOME DISTANCE DOWN.

  +A. Glabrous--i.e. with no obvious hairs[7].+

    (_a_) Grasses with setaceous or bristle-like leaves;--i.e. the
          lamina of the lower leaves remains permanently folded instead
          of opening out flat.

      (1) Ligule obsolete, auricled at the junction of blade and sheath.

_Festuca ovina_ (Sheep’s Fescue). Densely tufted perennial. Leaves
hard, glabrous and often glaucous, with 5-7 ridges if forcibly
unrolled, ears short, stiff and erect. Branches in permanent sheaths.
Chiefly useful as pastures on downs and dry chalk-soils. Several
varieties are recognised by agriculturists, as hard, red,
various-leafed, fine-leafed Fescue, &c. (see Figs. 13 and 18).

_Festuca Myurus_, L. (Rat’s-tail Fescue). Annual, longer auricles, and
hair on the ribbed inrolled surface. A road-side weed.

  _Festuca ovina_ presents difficulties with its varieties and with _F.
  Myurus_, L. (var. _sciuroides_, Roth.).

  The chief varieties of _F. ovina_ are Hard Fescue (_F. duriuscula_,
  L.), taller and with some of the upper leaves flat, and found in
  moister and rich soils: Red Fescue (_F. sabulicola_, Duf. or _F.
  rubra_, L.) more or less creeping and with red sheaths to the lower
  leaves, on poor stony land--_F. heterophylla_ is a form of this on
  chalky soils, with flat leaves above: and _F. tenuifolia_ a very wiry
  form on sheep-lands. They all pass into one another, however, and
  cannot be distinguished by the leaves (see Figs. 18-20).

  _F. Myurus_ (var. _sciuroides_) is ruderal and annual, and has longer
  hairs on the ridges of the folded leaves. It has no agricultural
  value.

      (2) Ligule membranous, not auricled.

        (α) _Bristle-like (setaceous) leaves, very hard and stiff,
            and more or less solid._

_Nardus stricta_, L. (Moor Mat-grass). Roots very tough and stringy:
ligule small, but thick and blunt. Leaves channelled: upper erect,
lower horizontal. Sheath smooth. Moors and sandy heaths: useless (Figs.
2 and 26).

_Aira flexuosa_, L. (Wavy Hair-grass). Roots fibrous. Leaves short,
filiform, terete, solid--the channel hardly discernible. Ligule short,
obtuse. Heaths, &c. Of little use, even for sheep (Fig. 28).

        (β) _Leaves bristle-like, but distinctly due to inrolling
            of edges._

_Aira caryophyllea_, L. (Silvery Hair-grass), is scabrid. A weed, with
very slight foliage.

_A. præcox_, L. (Early Hair-grass). Greener and more glabrous. Habit
more rigid.

_A. canescens_, L. (Grey Hair-grass). Glaucous or purplish; rare, on
S.E. coasts.

        (γ) _Leaves narrow and more or less involute, and subulate
            upwards, but easily unrolled, and apt to become flatter
            as they age._

_Avena pratensis_, L. (Perennial Oat). Leaves rather thin, dry, harsh,
ridgeless, with flanking lines and a keel[8]; glaucous, glabrous,
but edges scabrous. Usually involute, but may open out. Ligule long
ovate-acute. Dry pastures, especially on calcareous soil, and of little
value.

_Poa maritima_, Huds. (Sea-grass). Leaves narrow, rather short, and
U-shaped in section. Involute: ridgeless, with flanking lines, but no
keel; soft and rather thick. Ligule rather long, obtuse and decurrent.
Useless agriculturally.

  For difficulties with other species of _Avena_ and _Poa_ see pp. 44,
  54 and 60.

    (_b_) Grasses with the leaves expanded, more or less flat.

      (1) Blades conspicuously ridged--i.e. the surface is raised in
          prominent longitudinal ridges with furrows between.

        (i) _Leaves rigid and hard, sharp pointed. Sheath and outer
             leaf-surface usually glabrous._

_Aira cæspitosa_, L. (Tufted Hair-grass). Forms large tufts. A coarse
weed forming bad tussocks in wet meadows and pastures: useless for
fodder. Leaves flat. Ligule long, acute. Ridges equal, high and sharp,
and scabrid, with 5-6 white lines between, if viewed by transmitted
light. Wet meadows.

  _A. cæspitosa_ cannot easily be mistaken for any other species.
  _Alopecurus geniculatus_ is also a moisture-loving grass with
  strongly ridged leaves, but the interspaces are far less
  translucent and the whole habit is different.

  All the other species of _Aira_ have involute and setaceous leaves,
  and even _A. cæspitosa_ is apt to roll in its leaves in mountain
  varieties, but they are easily flattened out, and show the ridges.

_Psamma arenaria_, Beauv. (Sea Mat-grass). This is one of the most
valuable “sand-binders,” its long matted rhizomes holding loose sand
together. It is a sea-shore grass, of no use for fodder. It was
formerly much used for mats and thatching. Leaves concave, long,
narrow, erect, scabrid and glaucous above, and polished below: pungent.
Ridges rounded, alternately high and low. Sheath long. Ligule very long
and bifid.

_Elymus arenarius_, L. (Sand Lyme-grass). Like _Psamma_, this is a
“sand-binder” and of no use for fodder. Leaves concave, and eared at
the base of the blade: ears pointed and tend to cross in front. Ligule
very short and obtuse. Ridges flattened above, not scabrid. Apex of
blade rolled, forming a hard spine.

  _Psamma_ cannot easily be mistaken for the much less common _Elymus_,
  as it is not eared, and the ridges and ligule are very different.

        (ii) _Leaves not specially rigid and hard, and often thin;
             glabrous, or shining below. Ridges less evident._

          * _Ligule very short or obsolete; blade firm but not hard,
            glabrous or nearly so, and shining below. Sheath often
            coloured red or yellow at the base._

            † _Sections of sheathed leaves narrow, oblong, owing to
              compression of shoots. Sheath nearly entire._

_Lolium perenne_, L. (Perennial Rye-grass). Very valuable
pasture-grass, especially on clay. Less successful as hay. Deep rooted
tufts. Glossy dark green. Ligule short (Fig. 11). Sheath red or
purplish below. Blade conduplicate and keeled, often rounded, collared
or eared at the base; with rounded ridges and rough above, shining
below. When the ears are well developed their points often cross one
over the other in front of the sheath.

_L. italicum_, Braun. (Italian Rye-grass), is an earlier and better
variety for hay and sewage farms. Shoot more rounded in section, and
has less marked veins on the more rolled leaf.

_L. temulentum_, L. (Common Darnel), is annual and a weed of
corn-fields. Foliage usually rougher.

  _Lolium perenne_ presents some difficulties in relation to such forms
  as _L. italicum_, species of _Agrostis_ and _Festuca_, _Alopecurus
  pratensis_, _Cynosurus_ and _Agropyrum_.

  Owing to the leaves not being always strictly conduplicate in the
  first year, the flat shoots may not sharply mark it off from _L.
  italicum_. Its somewhat looser, almost stoloniferous tufts, and
  darker green foliage, less polished below and usually narrower and
  harder, have then to be taken into account.

  The ridges of _Lolium_ are often like those of _Festuca pratensis_;
  and the shining lower surface and rather firm leaves and red sheaths,
  present other points of confusion. The smooth basal margins of
  _Lolium_, absence of white translucent lines when held up, and
  the different ligule and ears afford distinctions--the ligule of
  _Festuca_ being a mere line, and the ears pointed and projecting,
  whereas they may be mere lateral ledges in _Lolium_.

  _Cynosurus_ has the ligule and ears very like those of _Lolium_, the
  ears being mere ledges; but the former has yellow sheaths, firmer and
  thicker leaves with more evident ridges, and the old plants usually
  have the characteristic crested spikes remaining. _Cynosurus_,
  moreover, has the sheath split only a short way down.

  With regard to _Agrostis_, there is no colour in the sheath, the
  ligule is longer and pointed, and the leaves drier and thinner than
  in _Lolium_, and harsher on both surfaces. _Agrostis_ has also no
  ears.

  _Alopecurus pratensis_ has much broader and flatter ridges than
  _Lolium_ and a longer ligule, and its sheaths are dark-brown or
  black--not red; but _A. agrestis_ has very similar ridges to _Lolium_
  and may easily be confounded at first.

  _Agropyrum_ is sometimes nearly glabrous, and may then be confused
  with _Lolium_ by beginners: its low ridges, curled and pointed ears,
  obsolete ligule, and thinner, drier, harsher blade, as well as the
  stolons, distinguish it.

  _Lolium temulentum_ and _Hordeum murinum_ occasionally cause
  difficulty, but the latter is always more or less hairy, its blades
  thinner and drier, and the ridges less raised.

            †† _Sections rounded--elliptical or nearly circular.
               Sheath distinctly split, at least above._

_Cynosurus cristatus_, L. (Crested Dog’s-tail). Useful as pasture on
dry soils, but only moderately so as hay. Blade narrow, slightly eared
or collared below, tapered above; firmer than _Lolium_. Sheath only
split a short way down. Yellow or yellowish-white at the base. Leaves
conduplicate or convolute, short and narrow, the ligule short: minute
ears at base. Usually easily recognised by the withered culms and
persistent pectinate spikes (Fig. 16).

_Festuca elatior_, L. (Meadow Fescue). A valuable meadow and pasture
grass, though somewhat coarse. Several varieties are known. Best
on heavy soils. Deep rooted. Blade flat and broad, conduplicate,
sharp-eared at the base, and there rough at the margin: lower surface
polished. Rich green. Mid-rib flat above, numerous ribs with white
lines between if held up and examined with a lens. Ligule obsolete
(Figs. 12 and 17).

_Arundo Phragmites_, L. (Common Reed). A large aquatic, reed-like
creeping grass, with broad leaves (3/4 to 1 in.), flat, rather rigid,
acuminate, glaucous below, hispid at edges. Sheath smooth, striate,
bearded at mouth. Ligule a mere fringe of hair. (Cf. _Digraphis_, p.
54.)

  _Cynosurus_ is not very liable to confusion; but it has resemblances
  to _Lolium_ (see p. 49) and to species of _Agrostis_. The leaves
  of _Cynosurus_ are firmer, thicker, less dry, and with a shining
  undersurface, and the sheath is only split above, and yellow below;
  whereas _Agrostis_ has relatively thin and dry leaves, rough surfaces
  and margin, distinct ridges, and converging margins as the blade
  nears the sheath.

  _Festuca elatior_ is easily confused with the glabrous Bromes. For
  _B. giganteus_ see p. 43.

  _Bromus erectus_ is distinguished by the entire sheath,
  usually hairy, the want of auricles, and the conduplicate--not
  convolute--leaves.

  _Agrostis_ has thinner, duller, and drier leaves, and no red sheath.

  _Alopecurus pratensis_ has more depressed, flatter and broader ridges
  than _Festuca_, and a longer ligule, and lacks the pointed ears.

          ** _Ligule whitish, membranous, long, or at least well
             developed. Sheaths not coloured or brown. Leaves
             thin and rough, at least at the base. Ridges not
             very prominent, but numerous and distinct._

_Agrostis stolonifera_, L. (Fiorin). Stolons, with numerous short
offsets bursting through the leaf-sheaths. Blade flat, rough, tapering,
with rounded ridges, and convolute in bud: there are no auricles, but
the blade may narrow, and form ledges, as it runs into the sheath.
Sheaths nearly smooth. Ligule long and pointed, and often toothed at
the margins. The leaves vary in breadth.

This and _A. vulgaris_, With. with shorter ligules, and, possibly, _A.
canina_, L. with finer leaves, are varieties of _A. alba_, L. Only the
variety _A. stolonifera_ is of moderate value for pasture, especially
on poor soils, as it lasts late into autumn: the others are weeds, like
couch-grass.

  _Agrostis_ is full of difficulties for the beginner. The weed-forms
  often spring up after wheat has been cut, and count as “twitch,” like
  _Agropyrum_.

  All the ordinary forms--_A. stolonifera_, _A. vulgaris_, and _A.
  canina_--may be included in _A. alba_ (Linn.). On dry hills a close
  tufted grass, with setaceous leaves, and in rich soils creeping and
  luxuriant with broad leaves. It is one of the few grasses that thrive
  in wet soils.

  The chief points in the flat-leafed forms are the thin, dry leaves,
  rough on both sides and on the margins, with distinct raised ridges,
  and the base of the leaf narrowing suddenly into its insertion with
  the sheath, with no auricle, but with a long membranous ligule. The
  sheath not coloured, and the blade convolute.

  Again, _A. stolonifera_ has a long, serrated, acute ligule, while _A.
  vulgaris_ has a much shorter, entire and truncate one, and narrower
  leaves.

  _Agropyrum_ is the grass most likely to lead to confusion. Its
  ears, lower ridges, very short or obsolete ligule, and pubescence
  (sometimes glabrous) distinguish it.

  _Cynosurus_ sometimes gives trouble (see p. 50) with _Alopecurus
  pratensis_: the sheaths, ligule and flattened ridges should suffice
  for distinction.

  _Alopecurus geniculatus_ is even more like _Agrostis_, but its ridges
  are more prominent and sharp, and its aquatic habit and bent “knees”
  distinguish it.

  _Alopecurus agrestis_, in dry corn-fields, has a thickened ligule,
  sometimes coloured, and is annual or biennial, but otherwise very
  like _Agrostis_.

_Alopecurus pratensis_, L. (Meadow Foxtail). Large grass with stolons;
very early, and much prized as pasture and hay, but soon dies out
on light poor soils. Especially good for stiff soils. Sheaths long,
ridged, brown or nearly black at the base as they age. Ligule distinct
and obtuse, entire. Leaves numerous. Blades long, dark green,
succulent and scabrous: ridges numerous and flat above, but distinct
(Fig. 9).

  _A. agrestis_, L. in S. England has shorter leaves, and ridges not
  flattened; it is a troublesome pest of arable land, but does not
  usually invade pasture.

  _A. geniculatus_, L. is semi-aquatic, and like the last. It is easily
  recognised by its sharply bent “knees,” and is of little value (Fig.
  3).

  _Alopecurus_ shows resemblances to _Lolium_ (see p. 49), _Festuca_
  (see p. 50), and _Agrostis_ (see p. 52). If well grown its ridged
  sheath and leaves, the former brown or black at the base, aid in
  distinguishing it.

      (2) Blades either devoid of ridges or with very inconspicuous
          ones.

        * _No trace of ridges, and the mid-ribs not prominent, but the
          leaves show median lines flanked by finer ones when held up.
          Blades thin and narrow. Somewhat keeled._

          (i) _Shoots compressed._

_Poa compressa_, L. (Flat-stemmed Meadow-grass). Leaves rather short,
more or less glabrous or glaucous, and +V+-shaped at the base; shoots
compressed, and naviculate in section. Ligule short and thin. Sheath
tends to be closed below. A creeping perennial on commons and waste
lands, and of little or no value.

_Poa annua_, L. (Annual Meadow-grass). Small annual. Compressed shoots,
limp. Leaves linear, pale, sub-acute, thin, often wavy, flat, flaccid,
bright green; dull or slightly shining and +V+-shaped in section below.
Ligule long, pointed, whitish and clasping the shoot. It is a harmless
weed, and since it puts out shoots all the year round, furnishes a
certain amount of pasturage.

          (ii) _Shoots terete or nearly so._

_Poa nemoralis_, L. (Wood Poa). Leaves and sheaths smooth. Blade bright
green, thin, often glaucous, linear-narrow, flaccid, acute. Ligule
almost obsolete. Section of shoots round. Of little value.

_Poa bulbosa_, L. (Bulbous Meadow-grass). Stems bulbous at the base.
Ligule long and acute. Leaves very narrow and tapering. Sections of
shoot round. Coasts of S. and E.

  All the Poas, except the aquatic ones (_Glyceria_) and _P. maritima_,
  have glabrous ribless blades with the median lines, and slight keel.

  _P. pratensis_, _P. alpina_ and _P. trivialis_ (Fig. 8) have
  entire sheaths (as have _Glyceria fluitans_, _G. aquatica_ and _P.
  maritima_), but the others have them split some way down.

  The leaves of _P. pratensis_ and _P. compressa_ are firmer than the
  thin leaves of _P. annua_, _P. trivialis_ and _P. nemoralis_.

  Sheaths flattened in _P. pratensis_, _P. compressa_, _P. annua_, and
  _P. trivialis_; but rounded in _P. nemoralis_. _Glyceria aquatica_
  and _G. fluitans_ have netted sheaths.

  _Poa annua_ is annual, and _P. bulbosa_ has the bulbous base. _P.
  maritima_ has involute leaves and no keel, and the rare _P. alpina_
  has short rigid keeled mucronate leaves, with tip often inflexed and
  thickened scabrid edges.

  The leaves of Avena are apt to appear similar to those of the Poas
  at first sight, but the former are hairy, and ridged, dry as well
  as thin, and the peculiar median lines of _Poa_ are wanting. _Poa
  bulbosa_ has drier leaves than usual, but its leaves are devoid of
  ridges.

        ** _Ridges can be detected, but are slight and not distinct.
           Margins scabrid, at least at the base._

          † _Leaves firm, flat, linear, acuminate, not narrowed
            below. Glabrous. Ligule membranous._

_Digraphis arundinacea_, Trin. (Reed-grass). Sheathed leaves round
in section; blades convolute, tapering above, flat, firm, long and
broad (1 in.) below. Mid-rib and veins numerous, and prominent below.
Stoloniferous: branches extra-vaginal, often with deep red basal
scales. Sheaths with much overlapping membranous margins, with a
collar-like ledge above. Ligule long and somewhat acute. Wet ditches,
&c., of no value (Figs. 7, 14).

  For distinction between _Digraphis_ and _Dactylis_ see p. 41. _Poa
  pratensis_ is at once distinguished by its flattened shoots, more
  rounded leaf apex and shorter ligule. _Arundo Phragmites_ is easily
  distinguished by the ligule (see p. 51), and the other aquatic
  grasses are quite different (see p. 39).

_Phleum pratense_, L. (Timothy-grass). No stolons, but bulbous on
dry ground. Early, and a heavy cropping hay grass: also excellent
pasture; branches intra-vaginal, but burst the glabrous sheaths.
Old sheaths fibrous. Leaves short, convolute, with scabrid margins
owing to deflexed teeth: ridges obsolete above, no keel; broader and
greyer green than _Alopecurus_. Ligule short on radical leaves, thin.
Pastures. Perennial.

  The smooth ligule, deflexed marginal teeth, and no keel distinguish
  it from _Arrhenatherum_.

_Phleum arenarium_, L. (Sand Phleum). Shoot annual, with no bulbs.
Leaves broad, flat and glabrous, but rough at the edges, with
descending teeth. Ridges low and flat. Sheaths smooth: leaves
conduplicate. Ligule long. Sandy coasts, &c. A weed.

  _Phleum asperum_, Jacq. and P. _Bœhmeri_, Schrad. are rare ruderal
  plants, and _P. alpinum_, L. is confined to the Scotch Highlands. _P.
  arenarium_ is sharply distinct by its conduplicate leaves and habitat.

  _Alopecurus pratensis_ has narrower and less grey-green leaves than
  _Phleum pratense_, its ligule is shorter and blunter, its sheath
  more grooved and dark below, and the ridges more distinct and flat.
  It is relatively well rooted and is stoloniferous.

_Arrhenatherum avenaceum_, Beauv. (False Oat-grass). Loose tufts with
short stolons, or bulbous below. Leaves few, narrow, thin, dry, rough,
with very low flat ribs, convolute in bud, and practically glabrous.
Sheath smooth. Ligule truncate, hairy on its outer surface. Bitter, and
commonly undervalued by agriculturists, but useful in mixed pasture,
and yields bulky, coarse hay.

  There are often a few sparse isolated hairs on the low ribs. The base
  enters the sheath with slight and sometimes pinkish ledges. Ridges
  hardly observable. Traces of roughness if rubbed downwards. White
  lines, about 5 each side on holding up to the light. The not very
  long leaves taper slightly below.

  _Arrhenatherum_ is liable to confusion with _Holcus_, _Anthoxanthum_,
  _Molinia_ and _Avena_, but it is typically glabrous, whereas the
  others are hairy.

  From _Holcus_ it is easily distinguished by the sheaths, ligule and
  soft hairs of that genus.

  _Anthoxanthum_ differs in its habit, ears, scent, sheath and ligule.

  _Molinia_ differs in habit, ligule, sheath, and tough stringy roots,
  and the shape of the leaves.

  _Avena pratensis_ differs in its narrow leaves, less prominent
  ridges, and ligule; _A. flavescens_ in its much broader and coarser
  hairy leaves, and the ligule; and _A. pubescens_ in pubescence and
  flat-shoots and ligule.

          †† _Leaves very thin, blade tapering below. Keel
       prominent, but no ridges above. Ligule long and torn._

_Milium effusum_, L. (Spreading Millet-grass). Tufted perennial. Leaves
linear-lanceolate, scabrid above. Sheath smooth. Bitter tasting. May be
slightly hairy. Woods. It is much liked by birds, but is of no value in
agriculture.

  +B. Leaves or sheaths, or both, distinctly hairy.+

    (α) Leaf-blades eared at the base.

      (_a_) Ears sharply pointed. Leaves convolute, and sections
            of shoots round. Ligule short and inconspicuous.

_Agropyrum repens_, Beauv. (Couch-grass). A troublesome weed of arable
land and gardens, &c., owing to the extraordinary vitality of its
underground stolons. The young shoots are readily eaten by stock.
Perennial, and extensively stoloniferous; bright or glaucous green.
Blade thin, dry, rough edged, hairy and rough above, glabrous or
hairy below. The short ligule fringed. Ears long, or sometimes short,
pointed; often obliquely crossing in front of the sheath. Ridges
inconspicuous. Hairs may be absent from the sheath, and nearly so from
the blade.

  The sea-shore varieties are stiffer and more glaucous, the leaves
  more ribbed, involute and pointed--e.g. _A. junceum_, Beauv.

_Agropyrum caninum_, Beauv. (Bearded Wheat-grass). Tufted weed, not
creeping, in woods, &c. Blade thinner and rougher beneath, but very
variable. Properties similar to those of _A. repens._

  _Agropyrum_ may be confused with _Lolium_ (see p. 49) and _Agrostis_
  (see p. 51), but hardly with any other grass, and with these only
  because it is liable to be glabrous or nearly so on poor soil.

  _Elymus_ has much more pronounced ridges than the sea-shore varieties
  of _Agropyrum_.

      (_b_) Base of blade with inconspicuous rounded ears. Leaves
            convolute. Ligule conspicuous.

_Anthoxanthum odoratum_, L. (Sweet Vernal-grass). Compact tuft. Common
in pastures and hay, but it only forms a small proportion of the crop.
One of the earliest grasses, and the principal one, which gives the
scent to new-mown hay: a perfume has been extracted from it. Its value
as fodder is probably overrated. Bitter tasted. Leaves more or less
hairy at margins, especially at throat of sheath, flat, and slightly
ridged. Sheath furrowed, often pubescent. Ligule long and blunt, with
ciliate margins. Sweet scented when dried. The most shallow rooted of
all meadow-grasses. Leaves often short and few.

  _Anthoxanthum_ is sometimes confused with _Arrhenatherum_ (see p. 56)
  and _Molinia_; the latter differs in its ligule--a tuft of hair--its
  stringy roots, tapering leaf-base, less obvious ridges, and smooth
  sheaths, &c.

  _Anthoxanthum_ is deep green and often very luxurious in rich wet
  soils--e.g. in Devonshire.

      (_c_) Ears as mere collar-like ledges where the blade joins
            the sheath. Sheath usually pubescent or hispid with
            reflexed hairs. Ridges inconspicuous. Ligule very
            short.

        ✲ _Perennial, with firmer leaves_.

_Hordeum sylvaticum_, Huds. (Wood Barley). Leaves flat, thin but firm,
rather broad, scaberulous. Sheath hispid, with reflexed hairs. Blade
not tapering below. Translucent spaces between the veins as broad as
the latter. Ligule short and blunt. Shady places. Useless.

_Hordeum pratense_, Huds. (Meadow Barley). Tufted, or bulbous below.
Leaves narrower, flat, tending to roll up, scabrid above and hairy
beneath. Sheath narrow, hairy. Moist meadows, and of some use as
pasture in the young state.

        ✲✲ _Annual, with thin dry leaves_.

_Hordeum murinum_, L. (Wall Barley). Coarse tufts; leaves small,
narrow, hairy or scabrid. Sheaths sparsely hispid, or very downy,
inflated. Roads, &c. A useless weed.

  _H. maritimum_, With. is a sea-side form, smaller and more glaucous.
  Sheaths hairy.

    (β) Leaf-blades not eared at the base.

      * Sheaths of radical leaves veined with red-purple.

_Holcus lanatus_, L. (Yorkshire Fog). A useless weed, but very common
in pasture and hay; forming tussocks, greyish-green, softly hairy
(tomentose). Blades with roundish ridges. Ligule short and obtuse.
Sheath somewhat keeled, with trace of collar ledge. It is said to have
a bitter taste (Fig. 15).

  Ligule pilose. Tufted hairs along the broad rounded ridges, and on
  the lower surface and prominent keel.

  The much rarer _H. mollis_, L. is not so long-haired, except on the
  nodes, and is more creeping and slender in habit. It is a “twitch.”

  The Hordeums present several points of difficulty to beginners. The
  differences between the species are given above. _H. maritimum_ has
  narrower and thicker leaves than the rest.

  Bromes are most likely to be confounded with Hordeums, but they have
  entire sheaths and no ears (see p. 43).

  For distinctions between _H. murinum_ and _Lolium_ see p. 49. _H.
  sylvaticum_ and _Bromus asper_ (p. 44).

      ** No conspicuously red-veined sheaths.

        † Ligule absent, or a tuft of hairs.

_Molinia cærulea_, Mœnch. (Purple Molinia). Tussocks, with tough
stringy roots. Leaves narrowed below, and tapering above to a long
point, ridges obsolete; very thin and dry but fairly stiff, and hairy
above, especially at the base. Ligule absent, or a tuft of hairs.
Sheaths smooth. Moors. Useless as forage, but used locally for brooms.

  _Molinia_ is not easily confounded with any others but _Anthoxanthum_
  (see p. 57), _Arrhenatherum_ (see p. 56) or _Brachypodium_.

  _Brachypodium sylvaticum_ is distinguished by habitat, its broad
  leaves, membranous ligule, fibrous roots, &c.

_Kœleria cristata_, Pers. (Crested Kœleria). Very short,
perennial in dry pastures, pubescent, pale green. Leaves narrow,
tapering below, soon involute, ciliated. Ridges prominent, alternately
high and low. Ligule obsolete, or a mere jagged yellowish line. Useless.

_Triodia decumbens_, Beauv. (Decumbent Heath-grass). Low perennial.
Leaves narrow, obtuse, slightly ridged, tough, at length involute, with
long, soft hairs, especially below and on the edges. Sheath grooved,
hairy, especially at the throat. Ligule a tuft of hairs. Section of
shoot flat; leaves conduplicate. Of no known use as fodder.

  The rare grasses _Panicum glabrum_, Gaud., _P. viride_, _L._ and _P.
  Crus-galli_, L. introduced in the S.E. counties also come here.

        †† _Ligule membranous._

_Avena flavescens_, L. (Yellow Oat-grass). Loose tufted perennial,
pale green, with rounded shoots bursting the sheaths. Leaves flat,
slender, soft, fine-ribbed and hairy, especially on the low ridges
above. Sheath hairy, especially below, not keeled. Ligule short,
obtuse, often truncate, ciliate. A valuable pasture and meadow-grass,
also in water-meadows. Its roots are abundant, and it will grow well in
calcareous soils (see Fig. 10).

_Avena pubescens_, Huds. (Downy Oat-grass). A variety of _A.
pratensis_ (see p. 47), but less densely tufted, and the leaves flat
and pubescent, and especially the sheaths very pubescent. Ligule
ovate-acute. Shoots flat. Dry districts, and a weed.

  _Avena flavescens_ is not easily confounded with any other grass if
  well grown. All the Poas otherwise like it are glabrous, and without
  the ridges. The same applies to _A. pubescens_.

  _Arrhenatherum_ is also glabrous, its leaves narrower, its ridges
  much flatter and broader, and its ligule is hairy outside (see p. 56).

_Brachypodium sylvaticum_, Beauv. (Wood False-brome). Rather slender,
perennial. Leaves flat and devoid of ridges; long, very thin and dry,
limp, slightly tapering below, hirsute. Sheath round, hairy. Ligule
fairly long, obtuse, toothed. Copses, &c. Useless.

_Brachypodium pinnatum_, L. (Heath False-brome), is a species growing
in the open, with narrow, firm, rigid, erect leaves, hardly hairy; with
distinct ridges, and tending to roll up. Ligule fringed with hair. Open
heaths. Useless.

  The only grasses likely to be confounded here are the Bromes, and
  they have entire sheaths.




CHAPTER IV.

ANATOMY AND HISTOLOGY.


The principal anatomical features observed in the leaves of
grasses--apart from finer histological details into which it is
not my purpose to enter--concern the characters of the epidermis
and distribution of the stomata and hairs, the arrangement of the
chlorophyll-tissue, that of the mechanical tissue (sclerenchyma) and
the vascular bundles to which the venation and ribbing of the leaves
are due, and the presence or absence of those peculiar thin-walled
cells (motor-cells) which bring about the infolding or inrolling of
the lamina (see p. 25) as they lose water, and, finally, the presence
or absence of conspicuous lacunæ or air-spaces so characteristic of
aquatic species. Several observers have occupied themselves with these
matters, and the researches of Schwendener, Duval Jouve, Pfitzer,
Pée-Laby, and others have rendered it possible to group most of our
grasses according to the microscopic characters of the leaves, somewhat
as I have done in Chapter V.

Reference has been made to the rolling and folding of leaves, due to
the thin-walled cells on the upper surfaces capable of varying in
turgescence (motor-cells). These are specially adapted epidermal cells
found on the upper surfaces only. In the leaves of _Poa compressa_,
_P. annua_ (Fig. 21), _P. nemoralis_, _P. alpina_, _Catabrosa_,
_Sesleria_, &c., a row of these motor-cells, easily distinguished by
their large size, thin walls and clear contents, is found on each side
of the mid-rib; as they dry the leaf folds its two halves together
(conduplicate), and on the re-absorption of water they flatten the two
halves out again. In _Dactylis_ these flanking rows coalesce into one
over the mid-rib. In other leaves, e.g. _Avena pratensis_, _Festuca
elatior_ (Figs. 17, 22), _Melica_, _Elymus_ (Fig. 25), &c., there are
in addition to these two flanking rows, other sets of motor-cells
between the other ribs, and their combined action causes the halves of
the lamina to inroll, usually one-half inside the other--convolute.

[Illustration: Fig. 21. Transverse section of left-half of leaf of
_Poa annua_ (× about 50) showing keel below, and two flanking lines of
motor-cells (slightly shaded) above the median vascular bundle of the
mid-rib. Hence the leaf folds. The half lamina has six smaller vascular
bundles, only the stronger one girdered. Ridges practically obsolete
and subtending bands of sclerenchyma slight: hence the leaf-surfaces
are parallel.]

It is easy to observe leaves of such grasses as _Festuca pratensis_
(Fig. 22), _Aira cæspitosa_ (Fig. 23), &c., which are wide open in the
dewy mornings in summer, close up as the air gets dry and hot; and any
such leaf may be seen to roll up after plucking and can be reopened by
moistening it.

[Illustration:

  Fig. 22. Transverse section of left-half of leaf of _Festuca
  elatior_, var. _pratensis_ (× about 50). The ridges are well marked
  and flattened above. The vascular bundles of two orders are girdered
  below, but only slightly above. There is no keel. There are well
  marked motor-cells--not shown in the figure--in each groove.]

The epidermis of grasses has been closely investigated by Grob, but
unfortunately his results concern very few of our native species. The
principal elements are ordinary elongated cells, with plane or sinuous
walls, various kinds of short cells intercalated between the ends of
these, several forms of papillæ, hairs, &c. and stomata.

The epidermis over the parenchyma of _Digraphis arundinacea_ consists
of rectangular cells with plane walls.

Series or bands of long cells only may alternate with other series
where short cells intervene between the long ones--e.g. _Nardus_.

_Nardus_ has some of the bands devoid of stomata, but abounding in
short cells, whereas others (above) have stomata throughout.

In _Nardus stricta_, _Glyceria fluitans_, _Sesleria_, &c., there are
two kinds of short cells, some siliceous, others cutinized only.

_Nardus_ has closely appressed small 2-celled hairs bent at
right-angles, and some epidermal and parenchyma cells--especially below
the stomata--have solid masses of silica filling the lumina.

[Illustration: Fig. 23. Part of transverse section of leaf of _Aira
cæspitosa_ (× about 30). Ridges very high and acute, each tipped with
sclerenchyma, and containing an isolated vascular bundle--sometimes
one or more small ones also. Motor-cells well developed at the base
of each groove. The bundles are not girdered, but numerous bands of
sclerenchyma almost join into a continuous band below. The leaf rolls
inwards.]

Short cells occur in _Holcus lanatus_, _Hierochloe borealis_ and
_Dactylis glomerata_ interspersed between plane-walled cells.
They may be silicified and vary in shape--square, saddle-shaped,
elliptical, irregular, &c.; or they may be replaced here and there
by asperities--e.g. _Elymus_--or in rarer cases by stomata. Grob
has attempted the classification of their distribution in different
grasses, but the subject is too complex for treatment here.

The epidermis of many grasses is studded with short two-celled hairs
bent sharply at right-angles; so that the pointed or blunt, hollow or
solid, apical portion is appressed to the surface. Grob says that these
are absent from the Hordeæ, whereas 90% of the Panicoideæ and many
species of all other groups have them. Examples of the sharply pointed
form occur in _Nardus_, of blunt ones in _Cynodon_ &c.

In _Nardus_ they occur on the leaf surface both between and above the
veins, but in _Hierochloe_ &c. they are confined to the margins.

The following grasses have no hairs of either type:

  _Agrostis vulgaris_,
  _Calamagrostis lanceolata_,
  _Avena pratensis_,
  _Arrhenatherum avenaceum_,
  _Dactylis glomerata_,
  _Briza media_,
  _Arundo Phragmites_,
  _Glyceria fluitans_.

The sharp, hard prickle-hairs which give the pronounced roughness to
many leaves of grasses are longer than the foregoing, and stand off
more from the leaf. They occur both on the surface and at the margins,
and may be isolated--e.g. _Avena pratensis_,--or mixed with the short
cells--_Aira canescens_, _Elymus arenarius_. They are very abundant on
_Kœleria cristata_.

_Leersia oryzoides_ has asperities at the margin of the leaf with their
points directed upwards on the upper part of the leaf, downwards on the
basal parts, and the direction of such minute marginal asperities often
affords a useful distinctive character--e.g. _Phleum_, _Arrhenatherum_.
The marginal asperities in _Nardus_ are siliceous.

[Illustration: Fig. 24. Transverse section of part of leaf of
_Agropyrum junceum_ (× about 40) partly inrolled; showing unequal
ridges. The principal vascular bundles are girdered below, the
sclerenchyma joining into a strong continuous sheath. Each ridge is
tipped with sclerenchyma, and each groove has motor-cells--not shown in
the figure--below.]

Bristles--i.e. long, sharp, stiff hairs--are not very common. They
occur on _Nardus_, _Anthoxanthum Puelii_, _Panicum_, _Cynodon_.

Papillæ occur on the leaves of _Glyceria_, _Nardus_, _Leersia_, &c.

_Poa pratensis_ has soft hairs on the upper epidermis.

The stomata of _Sesleria cærulea_ are depressed and six-celled, two
guard-cells being overgrown by four accessory cells, but in most
grasses they are of the ordinary type with two elongated guard-cells
only.

[Illustration: Fig. 25. Transverse section of part of leaf of _Elymus
arenarius_, partly inrolled (× about 30), showing ridges of unequal
height, of which the higher are flat above. Vascular bundles girdered,
the stronger above and below. Motor-cells in each groove cause the
inrolling of the lamina by their contraction.]

As regards the vascular bundles constituting the venation, they are as
is well known parallel from base to apex in our common grasses, with
linear leaves, and are usually of four orders as regards strength.
Those of the first (e.g. mid-rib) and second orders have conspicuous
vessels, but those of the third and fourth orders may be practically
devoid of vessels, though xylem and phloem elements are always
present. Contrary to the general assumption, there are frequent though
minute transverse bundles joining the parallel veins.

The rule is that one vascular bundle runs up each mid-rib or ridge, but
exceptions occur--e.g. in _Arundo_ several bundles run up the mid-rib,
and in _Aira cæspitosa_ (Fig. 23) and others even the strong ribs may
have two or three bundles.

Each vascular bundle has its own sclerenchyma sheath, and very often
the stronger veins are accentuated owing to the vascular bundle
having a girder-like band of sclerenchyma running conjointly with
its sheath and joining the latter above and below--or below only--to
the epidermis (Figs. 24 and 25). In many cases these lower girders
spread out laterally below--fan-shaped in section--and nearly join the
neighbouring girders.

In other cases the strands of sclerenchymatous supporting tissue do not
join the bundles, but run parallel to them, above or below, as separate
strands just beneath the epidermis.

Finally, these strands may separate from the bundles, and fuse below
into a continuous layer under the epidermis; this occurs especially
in leaves of xerophytes where the cuticle is well developed--e.g. in
varieties of _Festuca ovina_ (Fig. 18), _Aira flexuosa_ (Fig. 28).

The distribution of the strands of isolated sclerenchyma affords
good characters. While there are none in _Mibora_, we find one large
strand at the ridge of the keel and one at each margin, in addition to
smaller ones subtending each vascular bundle, in _Avena pubescens_,
_Sesleria_, _Poa annua_ (Fig. 21), _P. bulbosa_, _P. compressa_ and
_Dactylis glomerata_. In _Festuca ovina_, _F. rubra_, _F. heterophylla_
(Figs. 18, 27) there are groups more or less pronounced at the keel and
margins, or even a continuous band below, but none above the bundles.

[Illustration: Fig. 26. Transverse section of leaf of _Nardus stricta_
(× about 50). The upper surface is represented by the four grooves and
five ridges, each of the former with traces of motor-cells at its base.
The deep shaded portions are sclerenchyma, strong girders of which
join the vascular bundle of each ridge to the lower surface. This type
is obviously derived from that in Fig. 19, and may be regarded as a
permanently rolled leaf.]

[Illustration: Fig. 27. Transverse section of leaf of _Festuca ovina_,
var. _duriuscula_ (× about 50), the type of a permanently folded leaf.
Seven ridges and six intervening grooves are seen: each of the latter
with traces of motor-cells below. In each ridge is an isolated vascular
bundle, and a narrow sclerenchyma band below.]

Many grasses have an isolated band above and below each primary bundle
only--e.g. _Panicum_, _Cynodon_--or above and below each of the other
bundles as well--e.g. _Spartina_, _Arundo_, _Polypogon_, _Agrostis
alba_, _Aira cæspitosa_ (Fig. 23), _Holcus lanatus_, _Glyceria
aquatica_, _G. fluitans_, _Digraphis_, _Elymus_ (Fig. 25), _Agropyrum_
(Fig. 24), _Brachypodium_, _Nardus_ (Fig. 26). In _Psamma arenaria_ the
lower bands join into a continuous layer.

In the following there is a band like a girder above and below each
bundle, and contiguous with it, joining it to the epidermis above and
below--_Leersia_, _Phleum pratense_, _Calamagrostis Epigeios_, _Bromus
erectus_, &c.

Güntz points out that xerophilous grasses are apt to have upright,
narrow (Figs. 26-28), grooved or folded leaves, with strong cuticle,
and marked motor-cells when the leaves open. It is in grasses of
this kind, especially such as inhabit dry sandy districts, that the
subulate, solid or grooved leaves shown in Figures 18, 19 occur--e.g.
_Festuca ovina_ and its varieties, _Aira flexuosa_, _Nardus stricta_,
&c. The epidermal cell-walls are sinuous, the stomata protected--e.g.
on the flanks of ribs and in grooves--and waxy or hairy coverings
occur. Colourless water-storing cells are apt to occur between or
around the vascular bundles, and the chlorophyll-tissues tend to
be dense and well protected inside the leaf: strongly developed
bast-sclerenchyma is also frequent (Fig. 18).

In shade-grasses, on the other hand, and in hygrophilous species, the
leaves are as a rule flat, with thin epidermal cell-walls, which have
plane sides, free stomata, and no wax &c. Water-storing tissue (apart
from tropical species) is sparse or absent, and the chlorophyll-tissues
have well aerated lacunar spaces. Bast-sclerenchyma is in these cases
feebly developed.

In the following chapter I have brought together some of the principal
anatomical features, in such form that the characters can be employed
in checking other determinations of grass leaves. The results, which
are based on the elaborate investigations of Duval Jouve, Schroeter,
Pée-Laby and Grob, as well as on my own observations, are not complete
in all respects, and much more should be done to extend the theme, but
the account given will serve to show the student how such results may
be employed. It is as yet impossible to decide how far these characters
are constant--they are known to be fairly so in many cases--but several
grasses cannot yet be distinguished by them alone.

[Illustration: Fig. 28. Transverse section of subulate leaf of _Aira
flexuosa_ (× about 50), the upper surface represented by a mere ridge
with two flanking grooves each with but traces of motor-cells below.
One large vascular bundle and four much smaller ones are seen. There
are no girders, but slender bands of sclerenchyma at the lower surface
nearly join into a continuous sub-epidermal sheath. This type is the
extreme form of that in Fig. 26.]

It should also be added that some grasses develope two types of leaves
(heterophylly), solid or subulate below, flat or slightly inrolled
above--e.g. _Festuca heterophylla_--and the following arrangement is
intended to apply to the vegetative lower leaves and not to those on
the upper parts of the flowering specimen. Moreover the sections should
be cut from the basal third of the lamina, and not from the tip of the
leaf.




CHAPTER V.

GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS OF THE LEAF.


  I. THE CHLOROPHYLL-TISSUE, ON TRANSVERSE SECTIONS, IS ARRANGED IN
  RINGS ROUND THE VASCULAR BUNDLES. THERE ARE MOTOR-CELLS BETWEEN THE
  RIBS, AND THE STOMATA ARE SUNK AND OCCUR ON BOTH FACES.

_Cynodon Dactylon._ The larger lateral nerves have as a rule three
smaller ones between each pair, hardly projecting as ribs. Chlorophyll
chiefly in a ring round the vascular bundle. Long hairs on lower
surface, a few papillæ above. Motor-cells in each shallow furrow. Short
cells occur between the long epidermal cells over the bast-region.

  The Panicums also come here, and differ according to the disposition
  of the sclerenchyma sheaths around the bundles.

II. THE CHLOROPHYLL-TISSUE IS BETWEEN THE VASCULAR BUNDLES, AND NOT
    CONFINED TO RINGS SURROUNDING THEM.

  +A. Conspicuous lacunæ between the vascular bundles. Stomata on both
  faces. Motor-cells occur.+

    Lacunæ large and rectangular. Motor-cells confined to a flanking line
    on each side of the mid-rib.

_Glyceria aquatica._ Leaves folded and in section +V+-shaped, hardly
keeled, with sclerenchyma at apex. Motor-cells each side of the mid-rib
only. The large square or rectangular lacunæ bounded by stellate cells.
Papillæ on epidermal cells. Vascular bundles midway between upper and
lower surfaces.

_Glyceria fluitans._ Section +V+-shaped and keeled, the roof of
each polygonal lacuna arched, hence the “ribs” on the upper surface
are between the vascular bundles. The latter lie nearer the lower
epidermis. The epidermis has papillæ.

  _Catabrosa aquatica_ and _Hierochloe_ also come here, the former with
  small lacunæ, the latter with larger ones chiefly towards the upper
  surface of the leaf.

  _Digraphis_ is also apt to have a few air cavities near the mid-rib.

  +B. Lacunæ none, or inconspicuous, the chlorophyll-tissue filling up
      between the ribs.+

    (_a_) Upper and lower leaf-surfaces parallel, or nearly so, and much
          alike, the ridges being very low or obsolete. Stomata equal or
          nearly so on both surfaces.

      (1) Motor-cells absent; vascular bundles feeble and very few.

_Mibora verna._ The small leaves are flat, or nearly so, and have
three isolated and very feebly developed bundles, devoid of girders or
sclerenchyma bands.

      (2) Motor-cells present, vascular bundles of various orders, with
          sclerenchyma bands or girders.

        * _Leaf keeled, and folded--not inrolled. Motor-cells confined
          to the neighbourhood of the mid-rib. No hairs._

          † _Motor-cells conspicuous and conjoined into a band above the
                mid-rib._

_Dactylis glomerata._ Keel pronounced, with one large vascular bundle
and a sclerenchyma band occupying its crest. Motor-cells forming one
conjoint band along the upper course of the mid-rib only. Stomata on
both faces, but no hairs or thick cuticle. Ribs low, and all bundles
have feeble girders. A little sclerenchyma at the margins. A few pale
cells in the chlorophyll-tissue.

          †† _Motor-cells inconspicuous and in two flanking lines, one on
                 each side of the mid-rib._

_Poa trivialis._ Keel with sclerenchyma at its apex, and a small band
of the same at the margins. Vascular bundles of three orders, isolated,
without girders, but with a small band of sclerenchyma above and below.
Ridges obsolete. Short hook-asperities above. No thickened cuticle.

  Other species of Poa also come here: I cannot distinguish them by the
  leaf anatomy; but _P. annua_, _P. compressa_, _P. nemoralis_ and
  _P. pratensis_ are devoid of the hooked asperities; _P. nemoralis_
  has a thicker lamina than the rest, and girders to the secondary
  bundles. _P. annua_ agrees in the latter point.

        ** _Leaf not keeled: rolling up. Motor-cells distributed
           between the ridges._

          † _Hairs none or rare, or at most a few asperities._

            ≡ _Veins numerous, 30-40 on each half lamina. Motor-cells very
              large._

              ⊙ _All vascular bundles with girders above and below._

_Digraphis arundinacea._ No keel. Marginal sclerenchyma conspicuous.
A few asperities below. Leaf thin, and all the bundles joined to
the epidermis above and below by girders (Fig. 14). Stomata on both
surfaces, fairly large: epidermal cells with plane walls. There may be
a few irregular air cavities, especially near the mid-rib.

              ⊙⊙ _Only the principal bundles girdered._

_Arundo Phragmites._ Ridges very numerous and low. No keel. Marginal
sclerenchyma strong. Vascular bundles with sheaths of large colourless
cells, a few of the strongest girdered below, but most have only
sclerenchyma bands above and below. Motor-cells particularly large,
between all the bundles. There are no conspicuous lacunæ. Hairs very
rare. Epidermal cells small, with sinuous walls: all the cell-walls
contain silica. Stomata on both faces, sunk, small and more difficult
to see than in _Digraphis_, where the epidermal cells are plane walled,
or nearly so.

  _Arundo Donax_ is very like _A. Phragmites_, but has larger bundles
  each with a horse-shoe shaped sclerenchymatous mass below, and larger
  lacunæ.

            ≡≡ _Veins not more than 10-20 in each half lamina._

              ⊙ _More or less conspicuously hairy. The smaller bundles
                isolated and devoid of girders._

_Bromus sterilis._ Girders to the stronger bundles only. Stiff hairs
above and below. Motor-cells poorly developed between each pair of low
ridges. No pronounced cuticle. A faint sclerenchyma-band at margin, and
at apex of low rounded keel. Stomata on both faces.

_Bromus arvensis._ Similar to _B. sterilis_, with stiff hairs commoner
below. Harsh in cutting.

  _B. giganteus_ shows no hairs, but I cannot distinguish the Bromes
  generally by the leaf anatomy.

_Anthoxanthum odoratum._ No keel, ridges obsolete, the stronger bundles
only with girders. Motor-cells conspicuous between all the ribs.
Marginal sclerenchyma, and that above and below the bundles, poorly
developed. A few coarse hairs both above and below, and stomata on both
faces. Leaf thin and narrow.

_Hordeum murinum._ Few girdered bundles, and sclerenchyma at margins
poor. Hairs sparse and coarse.

_Bromus asper_, _Brachypodium sylvaticum_ and _Lagurus_ also come here.

  In all these grasses the epidermal cells are chiefly long,
  rectangular or slightly hexagonal, with thin and plane walls.

                ⊙⊙ _Hairs none or very rare on the sections._

_Phleum pratense._ Low rounded ribs with motor-cells between. The
larger vascular bundles girdered. Stomata about equal on both faces. No
hairs. No keel. Marginal sclerenchyma scanty.

_Arrhenatherum avenaceum._ Very rare hairs above: a few blunt
asperities here and there. No keel. Ridges low. Girders to the primary
bundles, but not very strong: marginal and other sclerenchyma faint,
as is also the cuticle. Stomata on both faces. Motor-cells fairly
developed between the ridges.

_Briza media._ No keel, and mere traces of marginal sclerenchyma.
Ribs practically obsolete, but well developed motor-cells in furrows.
Principal bundles girdered. Stomata on both sides. No hairs or
thickened cuticle.

  _Avena fatua_, _Molinia_ and _Leersia_ also come here.

    (_b_) Upper and lower leaf-surfaces dissimilar, or at least not
          parallel, owing to the conspicuous ridges and grooves above.

      (1) No stomata below.

        * _Leaves flat or nearly so, or at least exhibit a conspicuous
          concave upper surface._

          ⊙ _Motor-cells between each pair of ribs: sclerenchyma not
            forming a continuous layer below._

            ≡ _Ridges at least 5-6 times as high as the leaf-thickness
              between._

_Aira cæspitosa._ Ridges high, 7-10 times as high as the breadth of
leaf between, triangular, each with 1-3 vascular bundles devoid of
girders, with an upper isolated band of sclerenchyma at the acute tip,
and another below the principal bundle. Also small bands below each
group of motor-cells. Small conical asperities on the ridges and below.
No mid-rib. Stomata on flanks of ridges only, and few motor-cells
between (Fig. 23).

Each vascular bundle has a sheath, but is isolated. Sclerenchyma at
tips of the ridges dense: smaller bands below: strong at margins. Lower
cuticle strong. Leaf rolls up.

  The flat upper leaves of _Festuca rubra_ (Fig. 20) and _F.
  heterophylla_ are somewhat similar in type. They have stiff hairs on
  the ridges.

            ≡≡ _Ridges not more than 2-3 times as high as the tissue
               between; each furrow with motor-cells, and each vascular
               bundle joined to epidermis above and below by a
               sclerenchyma girder._

_Brachypodium pinnatum._ Smooth. Ridges rounded. Hairs rare. The strong
sclerenchyma girders below almost continuous laterally. Epidermal cells
with sinuous thick walls, and a few tooth-hairs.

  Note the differences from _B. sylvaticum_, p. 76.

  _Melica nutans_, _M. uniflora_, and _Calamagrostis Epigeios_ also
  come here.

          ⊙⊙ _Motor-cells confined to the innermost 2-4 furrows.
               Sclerenchyma in a continuous band just inside the thick
               cuticle below._

_Festuca duriuscula._ The ridges are only about half to one-third
as high again as the thickness between, and the motor-cells in four
series at the base of the three innermost ridges. Each ridge has only
one isolated sheathed bundle, without girders. Stomata on the flanks
of the ridges, and few in number. The sclerenchyma forms a thick band
just inside the strong cuticle below. The leaf is conduplicate, not
convolute.

  This applies particularly to the more open leaves: the subulate
  leaves belong to the next type (see Fig. 27).

  _Aira canescens_ and _Spartina stricta_ also come here.

_Psamma arenaria._ Inrolled. Smooth below and devoid of keel, with
sub-epidermal band of sclerenchyma, and similar tissue at the margin.
Ridges of three sizes, the largest twice or three times as high as
the leaf-tissue between is thick, all rounded above, and very hairy.
Stomata above only. Motor-cells in each sinus not large. Vascular
bundles isolated, without girders or bands of sclerenchyma.

_Elymus_ is very like _Psamma_, but has a few stomata below and the
sub-epidermal sclerenchyma is not continuous (see Fig. 25).

        ** _Leaves (subulate) not opening out, the upper surface represented
           by a groove or a few ridges above the angular or ovate solid
           section._

          ⊙ _Section pentagonal or angular-ovate: sclerenchyma below in a
            continuous band._

_Aira flexuosa._ Upper surface a depression, with one ridge flanked
by two grooves at its base, the depression extending about one-fifth
through the whole thickness of the nearly solid leaf. Vascular bundles
about 3-5, isolated, sheathed. Sclerenchyma band extending all round
the lower surface just inside the thick cuticle. Stomata very few,
flanking the ridge; motor-cells in the furrows, poorly developed (Fig.
28).

          ⊙⊙ _Section elliptical or angular-ovate; sclerenchyma not always
                 in a continuous band below._

_Festuca ovina._ Upper surface a deep fold, with three ridges and
2-4 grooves at its base. Vascular bundles several, with girders.
Motor-cells in four series, in the grooves. The lower girders may not
fuse laterally into a continuous band of sclerenchyma below (Fig. 18).

  The folded lower leaves of _F. rubra_ and _F. heterophylla_ come here
  also. For the flatter leaves of _F. duriuscula_ see p. 78 and compare
  Fig. 27.

  The epidermal cells in this series have sinuous thickened walls, and
  here and there small tooth-like hairs.

  _Nardus_ also comes here (see Fig. 26).

      (2) There are stomata below, but fewer than on the upper surface.
          Motor-cells usually conspicuous between the ridges.

        * _Stronger bundles with girders of sclerenchyma joining them
          to the epidermis, at least below._

          ⊙ _Hairs sparse or none._

_Cynosurus cristatus._ Mid-rib obsolete, except the strong vascular
bundle. Ridges low and rounded, with 2-4 flanking stomata, and well
developed motor-cells in furrows. Secondary vascular bundles with
strong girders below, the smaller bundles sheathed only and isolated.
Each ridge with slight sclerenchyma above. A few stiff short hairs
above, and the leaves are convolute. Ridges about twice the height of
the leaf-thickness between (Fig. 16).

_Agropyrum repens._ Mid-rib and margin with strong sclerenchyma-groups:
ridges unequal, low and rounded and each vascular bundle girdered. A
few pointed hairs above, and motor-cells in all the grooves. A slight
keel, stomata on both surfaces.

_Agropyrum caninum._ All the bundles have girders. Slight keel.
Marginal sclerenchyma. Few, very short, hard, hooked asperities above
and below. Ridges low, and motor-cells poorly developed between. Few
stomata on lower surface. Very like _A. repens_, but the principal
ridges are more prominent below and those nearer the mid-rib have
asperities.

_A. junceum_ resembles _Psamma_, but the ridges are much lower, and
there are a few stomata on the under surface (Fig. 24).

          ⊙⊙ _Leaf obviously hairy._

            † _Hairs more especially above._

_Avena flavescens_ is very similar to _Cynosurus_, but is evidently
hairy, and _A. pratensis_ also comes here.

            †† _Hairs abundant on both surfaces._

_Holcus lanatus._ Very hairy above and below, and at the margins.
Slight keel with sclerenchyma band: sclerenchyma at margin slight.
Ridges rounded, about twice as high as thickness between. Stomata more
abundant above. Cuticle very thin and leaf soft. All bundles except the
mid-rib with girders. Motor-cells fairly well developed between the
ridges (Fig. 15).

_Kœleria cristata._ Very hairy on both surfaces. Ridges irregular,
the largest flat and high, the others rounded or triangular. Vascular
bundles isolated, and the sclerenchyma reduced to a few cells in a
single layer beneath the epidermis at the apex of each ridge and below
the bundle. Motor-cells well developed in each furrow. Stomata more
numerous above.

        ** _No girders to the vascular bundles._

_Lolium perenne._ Ridges numerous and unequal. Vascular bundles
sheathed and isolated--i.e. devoid of girders: small patches of
sclerenchyma at the apex of each stronger ridge, and on the opposite
side below only. No hairs.

  _Lolium temulentum_ is similar but is more apt to be convolute,
  whereas _L. perenne_ is more folded.

_Alopecurus pratensis._ Leaf thin and somewhat like _Phleum_, but the
ridges somewhat higher and more rounded, and only the principal bundles
girdered below. Stomata on both faces.

  _Festuca elatior_, _Bromus giganteus_ and most species of _Agrostis_
  come near _Lolium_. See Figs. 17, 22.




CHAPTER VI.

GRASSES IN FLOWER.


When the flowering shoot of a grass pushes up into the light and air
from the enveloping leaves, it forms a more or less branched collection
of flowers known as the _Inflorescence_, and in all our grasses this
inflorescence consists of a principal stalk, _haulm_ or _culm_, on
which shorter stalks--branched or not--are arranged. The mode of
branching is usually such that the youngest branches are nearest the
top, and the oldest nearest the bottom. It is evident at once, on
comparing the Moor Mat-grass (_Nardus_), Vernal-grass (_Anthoxanthum_),
Cock’s-foot (_Dactylis_), Meadow-grass (_Poa_) that considerable
differences exist as to the extent of this primary branching of the
inflorescence.

In _Nardus_ (Fig. 2) we find a number of long cylindrical-tapering
bud-like structures each seated on one side of the principal stem, and
one over the other: in the Vernal-grass and Cock’s-foot we find tufts
of such bud-like structures closely crowded round the upper end of the
principal stalk, the whole forming an elongated tuft of tufts: in the
_Poa_ we find a number of radiating, slender, long branches springing
from the principal stalk, and each of these ramifies again, and yet
again, until each of the ultimate hair-like branches bears one of the
bud-like structures. See also _Catabrosa_ (Fig. 4).

[Illustration: Fig. 29. A spikelet of _Festuca elatior_, var.
_pratensis_, from which the glumes and one palea (the outer) have been
removed to show the flower in situ (× 12). The two lodicules are in
front: the inner palea behind. Strasburger.]

The first thing for the student to apprehend is the nature of the
bud-like structures referred to.

Each of these is in itself a small tuft or bud of leaflike organs or
scales arranged on a short twig (_Rachis_, _Rachilla_), as it were, and
is called a _Spikelet_, and the true flowers of the grass are contained
in the angles between the scales--the scales being popularly known as
“_chaff_”: technically as _Glumes_ and _Paleæ_.

In order to understand the structure of a spikelet the student
should carefully dissect a large one, such as that of an Oat (Fig.
1). Proceeding from outside, he will find two large scales, like two
boats, fixed below to the stalk (_rachis_) one just below the other,
and shutting together as if hinged. These are called the _glumes_--the
inner and outer glume respectively--and they enclose the rest of the
spikelet.

[Illustration: Fig. 30. Diagram of a spikelet of a grass as it would
appear if the internodes between each set of organs were elongated.
_g^1_ lower and _g^2_ upper glume. _P_ lower and _p_ upper palea of the
second oldest flower _F^2_. _f_ a barren flower represented only by the
axis and paleæ. Above it a single palea and the termination of the axis
(_a_) of the spikelet.]

Inside them the axis or stalk (_rachis_) is continued for a short
distance only and on its sides are hinged two other pairs of more or
less boat-shaped scales, smaller and more delicate than the glumes, and
known as the _pales_ (_paleæ_), while a third pair of still smaller
pales is fixed to the end of the axis. In each case one smaller and
more delicate _inner_ palea is hinged just inside its more obvious
_outer_ palea. In the closed condition of the spikelet each of the
three pairs of pales is shut together, and pressed close to the axis,
and the pair of glumes shut in the whole.

On opening each of the lower pairs of pales we find a _flower_ inside;
but the terminal pair usually contain only the barren end of the axis.
Hence the latter is barren and the former are fertile.

Each fertile flower is found on careful dissection to consist of a
small swollen _Ovary_, or young grain, covered with silky hairs and
with a couple of delicate plumes (the _Stigma_) at its apex, and three
long and slender _Stamens_; while the magnifying glass will show two
tiny scales at the base--the _Lodicules_. All our ordinary grasses have
their flowers thus constructed--a pair of _lodicules_, three dangling
_stamens_ and an _ovary_ with a feathery two-plumed _stigma_: each such
flower is also enclosed in its pair of _pales_, and the several pairs
of pales of each spikelet, with their contents, are enclosed in the
pair of _glumes_ (Figs. 29-32).

Returning now to the inflorescence. It is clear that we have to
distinguish between the entire branched total Inflorescence, and the
Spikelets or partial inflorescences of which it is composed. In Botany
it is agreed to call any inflorescence consisting of a stalk or axis on
which the flowers are arranged without stalks--i.e. sitting directly
on it--and so that the youngest are above and the older below, a
_Spike_, and each spikelet is _a little spike_.

[Illustration: Fig. 31. Diagram of a spikelet of Wheat dissected (×
about 5) showing--from below upwards--the two glumes, two paleæ, two
lodicules, three stamens, and the ovary of the typical grass. Oliver.]

[Illustration: Fig. 32. Diagram of a spikelet of _Anthoxanthum_
dissected (× about 8), and showing--from below upwards--two outer and
two (awned) inner glumes, two paleæ, two stamens, and the ovary. There
are no lodicules. Oliver.]

On looking at the total inflorescence of the _Nardus_ we see that we
have a number of spikelets seated on the sides of an axis: this is then
a spike of spikelets, or, shortly, a _Spike_[9] (Fig. 5). _Mibora_ and
_Lepturus_ afford other examples. In _Panicum_, _Cynodon_ (Fig. 2) and
_Spartina_ we have groups of such spikes.

The _Poa_ inflorescence is, however, different. It consists of a loose
branched system of spikelets. Botanists term such a loosely branching
system, where each branch ends in a flower, a _panicle_: here then
we have a panicle of spikelets, or, shortly, a _Panicle_. _Aira_,
_Agrostis_, _Calamagrostis_, _Avena_, _Catabrosa_ (Fig. 4) and many
others afford further examples.

In _Dactylis_ we have a condition of affairs between the two extremes
given: the inflorescence is not so close a spike as _Nardus_, and
not so open a panicle as _Poa_--it is rather a spike-like panicle,
partaking of the nature of both. A special type of this (Foxtail)
occurring in certain grasses--e.g. _Phleum_, _Alopecurus_, _Phalaris_
and _Lagurus_,--is so characteristic as to be worth noting (Fig. 3).

There is also another aspect of these inflorescences which is not
without interest as showing how diagnostic characters may be obtained
from purely external features, easily observed in the field. We have
seen that in _Nardus_ the spikelets are arranged on one side only
of the rachis, or main axis, so that about three quarters of the
circumference of the latter is bare; whereas in _Lolium_--with which
_Agropyrum_ and _Brachypodium_ agree in this respect--the spikelets are
on opposite sides, leaving the intervening two quarters, i.e. half its
surface, of the circumference of the axis naked.

In _Cynosurus_ and the simpler forms of _Dactylis_, we find the
spikelets crowded round about three quarters of the surface of the
rachis, leaving the fourth quarter naked; and, finally, in _Phleum_,
_Alopecurus_, _Hordeum_, and _Anthoxanthum_ the spikelets cover the
entire surface.

In the first (_Nardus_) and third examples (_Cynosurus_, _Dactylis_)
where the spikelets are turned to one side, the inflorescence is said
to be _secund_.

The next point to notice is that not every grass has so many as two
fertile flowers and one barren one in its spikelet, as the Oat has.
A spikelet may have one (_Phleum_), two (_Aira_) or three (_Avena_)
or more (_Poa_) fertile flowers, and no barren ones or several, the
number of flowers being counted by the number of pairs of pales found
inside the pair of glumes. Moreover every flower is not necessarily
fertile (e.g. _Arrhenatherum_, _Holcus_) and several grasses have
one or more flowers in each spikelet containing _stamens_ only--male
flowers--while others may have _ovaries_ only--female flowers. In some
exotics the male and female flowers are on different parts of the same
plant (Maize) or even on different plants (_Gynerium_), an arrangement
not met with in our grasses. Accordingly, it is of importance in
determining a grass to discover how many flowers the spikelet contains,
and whether any are male only, or barren, &c., as well as to make out
the character of its inflorescence.

In the following lists I have brought together some of the chief points
with illustrative examples.


SPIKELETS with only one perfect flower (without rudimentary ones).

  _Psamma._
  _Milium._
  _Nardus._
  _Alopecurus._
  _Phleum._
  _Hordeum._
  _Agrostis._

And species of the rare grasses _Calamagrostis_, _Mibora_, _Lepturus_,
_Spartina_, _Cynodon_, _Gastridium_, _Lagurus_, _Polypogon_, _Leersia_.


SPIKELETS with one perfect flower and one or more male or rudimentary
ones.

  _Digraphis._
  _Anthoxanthum._
  _Holcus._
  _Arrhenatherum._

And the rare genera _Hierochloe_ and _Panicum_.


SPIKELETS with at least two perfect flowers.

  _Molinia._
  _Arundo._
  _Avena._
  _Aira_ (some species).
  _Bromus._
  _Cynosurus._
  _Dactylis._
  _Triodia._
  _Sesleria._
  _Kœleria._
  _Melica_ (one species).
  _Briza._
  _Poa trivialis._
  _Catabrosa._


SPIKELETS with at least three perfect flowers and usually more.

  _Elymus._
  _Agropyrum._
  _Brachypodium._
  _Lolium._
  _Festuca._
  _Poa._
  _Glyceria._


INFLORESCENCE, a spike of single spikelets.

  _Agropyrum._
  _Brachypodium._
  _Lolium._
  _Nardus._

And varieties of _Festuca Myurus_ and _F. loliacea_, &c.


INFLORESCENCE, a spike of pairs or tufts of three or more spikelets.

  _Elymus_ (pairs).
  _Hordeum_ (threes).
  _Cynosurus_ (clusters).


INFLORESCENCE, a cylindrical closely tufted spike-like panicle.

  _Phleum._
  _Alopecurus._
  _Psamma._
  _Anthoxanthum._


INFLORESCENCE, a compact more or less tufted panicle.

  _Molinia._
  _Kœleria._
  _Triodia._
  _Dactylis._
  _Aira præcox._
  _A. canescens._
  _Sesleria._

And rare grasses like _Polypogon_, _Gastridium_, &c.


INFLORESCENCE, a loose plume-like or branched panicle.

  _Avena._
  _Bromus._
  _Arrhenatherum._
  _Catabrosa._
  _Aira_ (except _A. præcox_ and
  _A. canescens_).
  _Arundo._
  _Digraphis._
  _Milium._
  _Agrostis._
  _Melica._
  _Holcus._
  _Poa_ (most of the species).
  _Glyceria._
  _Briza._
  _Festuca_ (except _F. Myurus_).

And the rare _Hierochloe_.

The _Glumes_ are always present in our grasses, and rudimentary only
in the rare grass _Leersia_; but _Lolium_ and _Nardus_ have only _one_
glume to the spikelet, and _Hierochloe_, _Digraphis_ and _Anthoxanthum_
(Fig. 32) have four or six. Our other grasses have _two_, but often
unequal in size.

In shape they are usually boat-like, pointed or obtuse (_Briza_) and
frequently with a distinct keel (_Anthoxanthum_, _Digraphis_, _Phleum_,
&c.) or with ridges, green lines (veins) and other characteristic
markings (e.g. _Digraphis_). The tip may be extended into a stiff long
point or awn (_Agropyrum_, _Phleum_, _Nardus_) and the keel, ribs,
and awn may have hairs or serrulæ on them. The rule is, however, that
the glumes are not awned. In texture the glumes may be herbaceous and
green-brown or purple (e.g. _Melica_) or membranous or stiff, or
scarious (i.e. browned, as if scorched) at the edges. In _Hordeum_ some
of the glumes are so narrow and pointed as to resemble stiff awns. In
_Catabrosa_ the glumes are truncate, as if bitten off at the top.

The _Paleæ_ are also often more or less boat-shaped, or flat ovate or
oblong scales, usually more delicate than the glumes and frequently
pointed, or (especially the outer pale) awned at the tip: in some
cases, however, the awn springs from the middle or base of the back of
the pale, and the latter may be bifid at its apex. The pale has usually
a distinct middle nerve. The inner pale is commonly the smaller and
more delicate of the two, and is sometimes difficult to see.


CONSPICUOUSLY AWNED GRASSES.

  _Avena._
  _Arrhenatherum_ (Fig. 33).
  _Hordeum._
  _Bromus._
  _Agropyrum caninum._
  _Lolium temulentum._
  _Brachypodium sylvaticum._
  _Festuca Myurus._

And a few rare grasses like _Panicum_, _Polypogon_, _Lagurus_.


GRASSES WITH NO TRUE AWNS.

_Kœleria. Milium. Digraphis. Elymus. Festuca_ (except _F.
Myurus_ and _F. uniglumis_). _Briza. Poa. Glyceria. Catabrosa._
_Molinia. Melica. Psamma. Agrostis alba._

And a few rare forms like _Leersia_, _Hierochloe_, &c.


GRASSES WITH INCONSPICUOUS AWNS, OR MERE POINTS, TO SOME OF THE GLUMES
OR PALES.

  _Arundo._
  _Phleum._
  _Alopecurus._
  _Holcus._
  _Nardus._
  _Agropyrum repens._
  _Lolium perenne._
  _Brachypodium pinnatum._
  _Dactylis._
  _Cynosurus._
  _Sesleria._

[Illustration: Fig. 33. _Arrhenatherum._ 1 unopened and 2 open anther
(× 12). 3, spikelets open and exposing the stamens and stigmas; 4,
the pollen escaping and being dusted on to the stigmas (× about 5).
Kerner.]

As regards the flower proper, all our British grasses except
_Anthoxanthum_ (which has two only) have three stamens; but many exotic
grasses have six stamens, and a few have a large number--even 40. The
stamens have slender filaments and large versatile anthers, which
dangle from between the paleæ when the flowers are mature, scattering
their clouds of fine pollen in the wind (Fig. 33).

All our ordinary grasses except _Nardus_--where there is a simple
straight hairy style--have two spreading feathery stigmatic plumes,
which stand out right and left from between the paleæ when the pollen
is flying about on the wind. (Fig. 33.)

Much interesting speculation has been expended in attempting to explain
the morphological or theoretical significance of the parts of the
spikelet of a grass. If we project the various organs on a flat surface
in the form of a plan, keeping their relative positions intact, we
obtain a diagram such as that shown in Fig. 34.

[Illustration: Fig. 34. Diagram of a spikelet of a grass. The two
glumes--_g^1_ outer, _g^2_ inner--embrace four flowers, of which 1 is
the lowermost and 4 the uppermost.]

The comparison of numerous cases, and the study of the development of
the parts on the microscopic growing point dissected out from young
buds, have suggested that the inner and outer glumes are bracts, or
covering leaves, at the base of the true spikelet. In like manner
the two paleæ are bracteoles which subtend the flower proper. On this
assumption they can be compared with the corresponding structures in
other plants; whereas any attempt to compare the paleæ or glumes with
the sepals and petals of ordinary flowers breaks down.

A curious interest attaches to the awns so often found on the backs of
paleæ, and especially to those where the (sub-terminal) awn springs
from just below the bifid apex (e.g. _Avena_, &c.).

Hackel showed by comparison with a rolled leaf attached to its sheath
and ligule (e.g. _Psamma_) that such an awn as that of _Bromus
Alopecurus_ attached to its palea stands in the relation of a leaf to
its sheath, the part of the palea above the insertion corresponding
to the ligule, the awn itself to the lamina, and the palea below its
insertion to the sheath. This view is rendered the more probable by the
anatomy of the awn and by the observations of Schmid, who has shown
that the awns of cereals contain chlorophyll-tissue and a vascular
bundle, and have stomata, and his experiments led him to conclude that
in the young condition they transpire and assimilate, and probably even
contribute to the nutrition of the ripening grain. When dry and mature
the awns subserve biological functions of quite another kind, and as
we shall see are of importance in the distribution and sowing of the
grains. (Fig. 42.)

Returning to the floral diagram, we see that the two lodicules, the
three stamens and the ovary still remain to be explained. Much
discussion has been held regarding the lodicules. Functionally
they are said to aid in the divarication of the paleæ when the
period of anthesis arrives, and the stamens and stigmatic lobes
are to be exposed, by swelling and driving the valve-like paleæ
apart. Morphologically they have been explained as representing the
rudimentary perianth, here reduced to two minute scales, but in some
exotic grasses (_Bambusa_, _Stipa_, &c.) three lodicules, or even
more, are present. (Figs. 35, 36.) On the other hand they may be, and
probably are, scales of the nature of minute bracteoles and of no
significance to the flower itself.

[Illustration: Fig. 35. Floral diagram of ordinary grass. Each pair
of paleæ--_i.p._ inner and _o.p._ outer palea--encloses three stamens
(_s_), two lodicules (_l_) and the ovary. _st_, stigmatic plumes. _a_,
axis.]

[Illustration: Fig. 36. Floral diagram of a Bamboo, showing six
stamens, three inner (_i.s._) and three outer (_a.s._), and three
lodicules (_l_) in addition to the ovary. _i.p._ inner and _o.p._ outer
palea. _a_, axis.]

If this is so the flower of the grass is perfectly naked, and consists
in the typical case of three stamens and one carpel. The development
of the ovary lends no support to the view that there are two carpels:
the stigmatic plumes are not separate styles. Nor does the fact that
some grasses have six stamens lend support to the idea that the flower
is derived from the trimerous type so common in Monocotyledons: other
numbers may occur--e.g. as few as two (_Anthoxanthum_, Fig. 32) or even
one only (_Uniola_, _Cinna_, &c.) or as many as 20 or 40 in certain
other exotic grasses.

Even when three stigmatic plumes are developed, as in some Bamboos,
close investigation does not confirm the view that the ovary consists
of more than one carpel.

We must therefore regard the flower of the grass as typically composed
of one carpel and three stamens, with no perianth whatever. It is
subtended by one or more bracteoles (the lodicules), and enclosed in a
pair of bracteoles one higher than the other (the paleæ). The glumes
are bracts of the partial inflorescence--the spikelet.

That there are some departures from this type in detail does not
invalidate the importance of the fact that most grasses conform to it.

I now pass to the consideration of a grouping of our ordinary grasses
according to their floral arrangements.

The student should distinctly understand that the following notes are
intended to serve as an introduction to the floral characters of our
grasses, and not to replace the study of the Flora. I have dealt
with this section of the subject less in detail, because our best
Floras give so much information that it seemed undesirable to do more
than attempt to guide the reader in the recognition of the genera and
principal species by means of external features easily observed by
anyone with a little care. The detailed and critical examination of
species, varieties and rare forms should always be done with reference
to a complete Flora.




CHAPTER VII.

GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES.


I. GRASSES WITH ONLY ONE PERFECT FLOWER IN THE SPIKELET.

  +(1) Inflorescence spikate[10].+

    +A. Inflorescence a spike of simple spikelets.+

_Nardus stricta_, L. A tough wiry tufted moor-grass, with setaceous
leaves, secund spikelets with a single rudimentary glume, and a stiff
simple hairy style. (Fig. 2.)

  The much rarer _Mibora verna_ about three inches or so high, and
  _Lepturus_, both with flat leaves, also come here.

  Certain superficial resemblances in the habit or inflorescence in
  _Festuca Myurus_ and rare forms like _Spartina_, may occasionally
  cause hesitation until the spikelets are examined.

    +B. Spike with sessile or sub-sessile tufts of three or more
        spikelets.+

      (_a_) A spike of tufted awned spikelets, in triplets at each
            notch of the rachis, and one or two of each triplet barren.

            +Hordeum.+

  No other genus of our grasses is like _Hordeum_. The purely
  superficial resemblances in the inflorescences of _Polypogon_,
  _Lagurus_, and _Cynosurus echinatus_--all extremely rare
  species--disappear at once on examination.

  In _Bromus erectus_ the equally superficial resemblance is due to the
  stiff awns: the spikelet has six to twelve flowers and is stalked.

  It should also be noted that _Hordeum sylvaticum_ occasionally has a
  rudimentary second flower in the lateral spikelets (see note p. 105).

        (α) A shade-grass with the central spikelet only imperfect;
           staminate, or rudimentary, or entirely wanting.

           _H. sylvaticum_, Huds.

        (β) The central spikelet is the perfect one, the two lateral
            barren. Growing in open land.

          (i) _A perennial meadow-grass. All the glumes scabrid and
              bristle-like._

              _H. pratense_, Huds.

          (ii) _Annuals with some of the glumes at least, lanceolate
               or broad below._

            * _Ruderal plant, with cylindrical spikes, long awns; glumes
              of the central flower dilated below._

              _H. murinum_, With.

            ** _Maritime plant, more or less glaucous, with short ovoid
               spikes: glumes of the central flower bristle-like._

               _H. maritimum_, With.

      (_b_) Spike cylindrical, of sessile or nearly sessile awned
          spikelets, densely crowded round the axis, the whole resembling
          a fox’s brush or cat’s tail.

  Species of _Lagurus_, _Polypogon_, _Phalaris_ (not truly awned),
  _Panicum_ (with bristles between the spikelets), and _Gastridium_ are
  other British grasses approaching this type of inflorescence: they
  are all rare or very local.

  _Sesleria_ has an ovoid spike, but the spikelets are two-flowered and
  not truly awned.

  _Kœleria_ may present resemblances, but the spikelets are very
  different in detail (see p. 109).

          (i) _Awns inserted into the back of the single palea,
              and hair-like. Glumes connate below, keeled. Only
              one palea._

              +Alopecurus.+

            * _Annual corn-weed, with a long and slender spike,
              pointed above. Glumes almost glabrous, and connate
              to the middle._

              _A. agrestis_, L.

            ** _Perennials, with shorter and stouter spikes, rounded
               above. Glumes connate at the base only, and obviously
               hairy on the keel._

              † _Procumbent and kneed at the nodes below.
                Spike 1-2 inches long. In marshy places._

                _A. geniculatus_, L.

              †† _A meadow-grass, with erect stems, and spikes
                 2-3 inches or more and stouter._

                 _A. pratensis_, L.

  The rare _A. alpinus_, Sm. with short ovoid spikes, about one inch
  long, only occurs in the Highlands.

          (ii) _Awns, when present, merely the stiff, pointed
               termination of the keel. Glumes free below. Paleæ two._

            * _A glaucous shore plant with long creeping stolons
              (sand-binder). Inflorescence harsh, 5--6 inches long.
              Glumes tapering, simply acute._

              _Psamma arenaria_, Beauv.

  _Elymus_, a much rarer sand-binder of similar habit, may lead to
  confusion until the 3--4 flowered spikelets and different arrangement
  are observed. (See p. 108.)

  _Agropyrum repens_ (var. _junceum_) is similar in habit and station,
  but its spikes and spikelets are very different (see p. 107).

  _Phleum arenarium_ is much smaller (see below).

            ** _Erect. Inflorescence rarely longer than three inches.
               Spikelets flat: glumes keeled, the keel suddenly produced
               into a sharp stiff awn or mucronate point. Paleæ two._

               +Phleum.+

              † _Tall perennial meadow-grass. Awn bristle-like, almost
                as long as the nearly glabrous glume: spike long,
                cylindrical._

                _P. pratense_, L.

              †† _Small, compact annual shore plant, with the glumes
                 acute only and the keel ciliate above. Inflorescence
                 not more than  1--1-1/4 inch long._

                 _P. arenarium_, L.

  The rare _P. Bœhmeri_, Schrad. has the glumes merely tapering to a
  sharp point; and the rare _P. alpinum_, L. has a much shorter spike
  and glumes ciliate on the keels.

  The rare _P. asperum_, Jacq. has broad, shortly mucronate glumes and
  a longer and more slender spike.

  +(2) Inflorescence a panicle--i.e. tufts or spreading stalked groups
       of spikelets are arranged on the main axis.+

    +A. Inflorescence compact and irregular; a spike of tufts
        (spike-like panicle). Glumes four, the inner pair awned: paleæ
        minute. Stamens two only.+

        _Anthoxanthum odoratum_, L.

  The four glumes and two stamens distinguish this grass at once. Other
  grasses with occasionally tuft-like inflorescences--e.g. species of
  _Agrostis_, _Gastridium_, _Aira_, _Dactylis_, _Cynosurus_, _Poa_,
  _Triodia_, _Kœleria_--are distinguished at once by having three
  stamens (_Bromus_ occasionally has but two), only two glumes, several
  flowered spikelets, &c.

    +B. Inflorescence a distinctly branched panicle, more or less loose
        and spreading.+

      (_a_) Tall reed-like perennials, growing in water or in marshes,
            with plume-like inflorescences, and silky hairs at the base
            of the paleæ. Glumes with a keel and point, but not awned.

        (i) Spikelets purplish: outer palea with a slender dorsal awn:
            basal hairs longer than the paleæ. Leaves narrow. Not common.

            _Calamagrostis Epigeios_, Roth.

        (ii) Spikelets greenish. No awns: basal hairs much shorter than
             the paleæ. Leaves broad. Common.

             _Digraphis arundinacea_, Trin.

  A variety of _Digraphis_ with white stripes in the leaves is grown in
  gardens. Other aquatic reed-like grasses are _Arundo_ and _Glyceria
  aquatica_: both have several flowers in the spikelet.

  The rare _Calamagrostis lanceolata_, Roth., _C. stricta_, Nutt. and
  _C. strigosa_, Hartm. also come here.

      (_b_) Slender grasses, not reed-like, with delicate loosely
            spreading panicles of small spikelets.

        (i) A tall, slender shade-grass, in woods. Paleæ very smooth and
            glistening. Spikelets few, distant and turgid, awnless.

            _Milium effusum_, L.

  _Melica uniflora_, also a wood-grass, has the spikelets two-flowered,
  though the upper one may be a mere rudiment, and much fewer, on a
  flexuous nodding axis. The much rarer _M. nutans_ has two perfect
  flowers in the spikelet (see p. 105).

        (ii) Grasses of open situations, with numerous small pointed
             spikelets. Inner palea minute or absent.

             +Agrostis.+

  The genus most likely to give trouble here is _Aira_, which though
  normally with two flowers in the spikelet, occasionally has but one.
  As regards the common species of similar habit, &c., _Aira_ has
  bristle-like leaves and _Agrostis_ flat ones.

  Again, _Agrostis alba_ has no protruding awn, as in the spikelets of
  _Aira_. For _Aira cæspitosa_ and other details, see p. 117.

          * _Awnless, or at most a short bristle not equalling the palea.
            Leaves flat and short._

            _A. alba_, L.

  An exceedingly variable plant. The variety _A. stolonifera_ has a
  less spreading panicle, and broader leaves with a long serrated and
  pointed ligule: the variety _A. vulgaris_ has a spreading loose
  panicle, narrower leaves, and a short truncated ligule. There is,
  however, much difficulty in distinguishing the intermediate forms on
  mountain-pastures, &c.

          ** _Distinctly awned. Leaves narrower, the lower ones inrolled
             and almost setaceous._

             _A. canina_, L.

  The rarer _A. setacea_, Curt. with subulate leaves and _A.
  Spicaenti_, L. with long awns also come here.

  The lax spreading type of panicle characteristic of _Aira_ and
  _Agrostis_, &c., described above, occurs in species of _Avena_,
  _Bromus_, _Briza_, _Poa_ and _Catabrosa_, but the basal silky
  hairs and twisted awns (_Avena_), long sub-terminal bristle-awns
  (_Bromus_), habit (_Catabrosa_), and the presence of two, three,
  or more flowers in the considerably larger spikelets of all, easily
  distinguish them.

  The rare grasses _Leersia_, with two glumes and no paleæ, and
  _Gastridium_, with curiously bullate bases to the glumes, also come
  into this group with one-flowered spikelets, but their characters
  must be studied with the flora. The same remark applies to species of
  _Panicum_, _Cynodon_, _Spartina_ and other aliens, occasionally met
  with.


II. GRASSES WITH AT LEAST TWO FLOWERS--OF WHICH ONE MAY BE
    IMPERFECT--IN THE SPIKELET.

  +A. Only one perfect flower, the other staminate only or altogether
      rudimentary. Inflorescence a loose or racemous panicle.+

  In _Hordeum sylvaticum_ the two lateral spikelets occasionally
  conform to this heading (see p. 100), and the same is said to be the
  case sometimes in _Aira_ (see p. 104). The rudiments are extremely
  minute, however, and hardly suffice to justify the removal of these
  grasses to this group.

  In one or two species of _Aira_ the panicle may be somewhat
  contracted and tuft-like.

  The very rare _Hierochloe_ has one perfect flower, and two lower
  staminate ones in each spikelet.

    (_a_) A shade-grass found in woods. Awnless. One flower perfect,
          the other (upper) reduced to a small stalked knob.
          Inflorescence racemous.

          _Melica uniflora_, L.

  The much rarer _M. nutans_ has two perfect flowers and a similar
  rudiment (see note, p. 104).

    (_b_) Grasses of open situations, spikelets with awns. The reduced
          flower staminate.

      * Upper flower perfect, lower staminate only. Tall oat-like
        meadow-grass, with a bent and twisted dorsal awn to the outer
        palea of the lower flower: silky hairs at the base of paleæ.

        _Arrhenatherum avenaceum_, Beauv.

  The grasses most like this are species of _Avena_ and _Aira_. The
  former have two or more perfect flowers, and the only broad-leafed
  _Aira--A. cæspitosa_, see p. 117--is easily distinguished by its leaves
  and its very small spikelets and short simple awns.

      ** Upper flower staminate: lower perfect. Small hairy grasses,
         with red-veined basal leaf-sheaths and short simple awns.

         +Holcus.+

        †  _Erect, evenly hairy, glumes blunt, awn not protruding.
           Common._

           _H. lanatus_, L.

        ††, _More or less procumbent, hairs chiefly at the nodes. Glumes
            pointed. Awns simple and exserted. Rarer._

            _H. mollis_, L.

+B. Each spikelet with at least two perfect flowers, often more.+

  (+1+) +Inflorescence spikate, the main axis bearing sessile or
        sub-sessile spikelets, each containing three or more flowers.+

    (_a_) Spike simple[11], axis stout and notched, each notch having
          one spikelet closely sessile in it.

      (_i_) Spikelets distichous, the flat side of each--i.e. the edges
            of the glumes--being next the axis (rachis).

            +Agropyrum.+

        * _A weed with creeping stolons, and no awns or mere points to
          the glumes._

          A. _repens_, Beauv.

  The variety _A. junceum_ found as a sand-binder on sea-coasts is
  glaucous, stiffer, with sharply pointed leaves, and blunt glumes. For
  other sand-binders see note, p. 102.

        ** _Not creeping. Awns long and prominent._

           _A. caninum_, Beauv.

          (ii) The rounded backs of the glumes are next the rachis.

            * _Spikelets flat and closely sessile in the notches of the
              rachis._

              +Lolium.+

              † _Awnless or nearly so. Perennial._

                _L. perenne_, L.

              †† _With conspicuous awns. Annual, not common._

                 _L. temulentum_, L.

  There are several cultivated varieties of _L. perenne_: _L.
  temulentum_ is notoriously poisonous (see note, p. 168). The
  lowermost glume of each spikelet is often alone developed or
  conspicuous, and looks like a bract in the axis of which the
  spikelet sits.

            ** _Spikelets elongated and hardly flattened, and not quite
               sessile, especially the lower: rachis scarcely notched, the
               spikelets with their sides (edges of glumes) next the axis._

               +Brachypodium.+

              † _A shade-grass with long, conspicuous awns to the more or less
                drooping spikelets. Common._

                _B. sylvaticum_, Beauv.

              †† _Growing in the open. Spikelets stouter, stiffer and more
                 erect, with short awns. Not common._

                 _B. pinnatum_, L.

  _Brachypodium_ may easily be confounded with _Bromus_, but the
  spikelets are nearly sessile: their shape and the absence of
  conspicuous notches distinguish this genus from _Agropyrum_.
  _Lolium_ has a conspicuously notched rachis and the spikelets
  arranged in the other plane.

  _Poa loliacea_, Huds., an uncommon sea-shore weed, may also be
  placed here; as also _Festuca elatior_, var. _loliacea_, Curt. and
  some forms of _Bromus arvensis_, var. _mollis_, L.

  No other British grasses resemble _Brachypodium_: any superficial
  likeness remarked in species of _Hordeum_, _Festuca_, &c.
  disappears at once on examination.

    (_b_) Spike compound--i.e. with clusters of two or more sessile or
          sub-sessile spikelets arranged along the rachis.

      (i) Spike elongated, fertile spikelets with 3-5 flowers.

        * _Pasture-grass with wiry rachis, on which the spikelets are
         secund and sessile in clusters: in each cluster a comb-like
         group of barren glumes subtends one of fertile spikelets._

          _Cynosurus cristatus_, L.

  The rare _C. echinatus_ has the pectinate groups of barren glumes
  even more prominent.

        ** _Stout glaucous sand-binder with pairs of spikelets sessile
           in the notches of the rachis, and all fertile. Spike
           cylindrical. Not common._

           _Elymus arenarius_, L.

  For other sand-binders see p. 102. The only grass likely to be
  confounded is _Agropyrum_, in which the spikelets are not paired.
  _Lolium_, _Brachypodium_, &c. are easily distinguished.

      (ii) Spike short and ovoid: spikelets sub-sessile and imbricate, in
           clusters. Bluish.

           _Sesleria cærulea_, Ard.

  Not easily mistaken for any other grass. As some of the spikelets
  are shortly stalked, the inflorescence is strictly paniculate, but
  the fact is not obvious. The glume-like bract at the base of the
  spike, and the general appearance suggest resemblances to certain
  moor-sedges at first sight. The only other grasses with similarly
  shaped spikes are species of _Alopecurus_, _Phleum_, and the rare
  _Lagurus_, _Polypogon_, _Phalaris_, _Panicum_, all with very
  different spikelets and easily distinguished.

  (+2+) +Inflorescence a panicle or raceme--i.e. the spikelets on
        evident stalks, simple or branched, from the main axis.+

  It does not follow that every spikelet is distinctly stalked, and
  cases occur where the stalks are very short and stiff: when this
  happens to the stalks arising from the main axis, and the latter
  is elongated, the type of the spike is closely approached, and the
  inflorescence resembles that of _Brachypodium_, _Lolium_, &c. In
  some depauperated varieties of _Poa_, _Festuca_, &c., an actual
  spike results (see note, p. 111): the number of flowers in the
  spikelet is important.

    _a_) Panicle short, contracted and tuft-like, owing to the
         shortness and stiffness of most of the stalks and their
         tendency to remain erect, at least until anthesis. Glumes
         keeled and ending in a point.

      (i) _Panicle with a few branches, at first erect, ending in
          tuft-like secund clusters. Spikelets harsh, with 3-5 flowers.
          Coarse meadow-grass._

          _Dactylis glomerata_, L.

  Not easily confounded with any other grass if attention is paid to
  the folded coarse leaves, the tufted perennial habit, and the harsh
  inflorescence, the glumes on the spikelets being stiffly hairy on
  the keel.

      (ii) _Panicle contracted, more or less ovoid or cylindroid, but
           most of the spikelets stalked, and not aggregated into dense
           clusters, spikelets silvery, containing 2-3 flowers._

           _Kœleria cristata_, Pers.

  Any resemblances to forms of _Aira_ are at once nullified by
  the absence of true awns in _Kœleria_. _Festuca_ and _Poa_ have
  more numerous flowers in the spikelet. _Anthoxanthum_ has only
  one flower, with two stamens, in the spikelets. _Phleum_ and
  _Alopecurus_ present resemblances, but see pp. 101 and 102.

    (_b_) Panicle elongated and lax--i.e. all or most of the spikelets
          on distinct slender stalks, longer than themselves.

      (i) _Panicle close: the spikelets on distinct and even long
          stalks, but the latter erect and keeping the spikelets near the
          main axis._

  In some cases the stalks from the main axis bear only one spikelet
  each and the type of inflorescence is that of a raceme; usually,
  however, one or more of the lowermost stalks branch and disclose
  the panicle.

        * Panicle with few simple branches, racemous, each spikelet large
          and containing about four flowers, palea three-toothed at the
          apex. A small heath-grass, with hairs at the ligule.

          _Triodia decumbens_, Beauv.

  The inflorescence may have some resemblance to _Melica_ (see p.
  105), but the four-flowered spikelet, ligule, habitat and stature
  distinguish it at once.

        ** Panicle with divided branches, which are more or less erect.

          † Spikelets awnless.

            ⊙ _Spikelets small, purplish, with two or at most three
              florets; the upper on a stalk. Coarse moor-grass._

              _Molinia cærulea_, Mœnch.

            ⊙⊙ _Spikelets with six or more florets._

              ‡ _Tall aquatic grass with long, lax, narrow panicle and
                spikelets, somewhat nodding, and with 8-20 flowers in
                each._

                _Glyceria fluitans_, Br.

The only similar grass is _Glyceria aquatica_, Sm. which differs in its
more reed-like habit, open panicle, and fewer flowers.

              ‡‡ _Small land-plants not more than a foot high, with
                 short, stiff, somewhat crowded panicles, and spikelets
                 containing 6-8 flowers._

                ≡ _Maritime perennial with creeping stolons, and about a foot
                  high: panicle somewhat open below._

                  _Poa maritima_, Huds.

                ≡≡ _Inland plant with secund panicle, about six inches high._

                   _P. rigida_, L.

  The rare _P. procumbens_, Curt. and _P. bulbosa_, L. also come
  here, as well as starved forms of _P. compressa_, L. Some forms
  of _Festuca elatior_, var. _pratensis_, Huds. growing in dry
  situations may give trouble, and will have to be examined with the
  flora. See also note, p. 109.

          †† Spikelets awned.

            ⊙ _Awns bristle-like and terminal on the paleæ: flowers
              about six in each spikelet. Leaves setaceous. Panicle
              secund._

              ≡ _Awns long and bristle-like. An annual weed._

                _Festuca Myurus_, L.

              ≡≡ _Awns very short, or merely the drawn out points of the paleæ.
                 Perennial._

                 _F. ovina._

  The rare _F. uniglumis_, Soland., and some other varieties may also
  come here.

  Some forms of _F. ovina_ are viviparous (see p. 134), and several
  varieties have to be distinguished.

            ⊙⊙ _Awns hair-like and dorsal on the paleæ. Flowers two
               in each spikelet. Annual, six inches or less in height._

               _Aira præcox_, L.

  The rare _A. canescens_, L. also comes here: its awn is jointed and
  with a minute tuft of hairs about the middle.

      (ii) _Panicle lax and open, the fine hair-like branches spreading
           widely during florescence, or even pendent or drooping._

        * Spikelets awnless.

          † A small aquatic grass with prostrate habit and two-flowered
            spikelets with broad truncate glumes and paleæ.

            _Catabrosa aquatica_, Beauv. (Fig. 4).

  The two-flowered spikelets distinguish it at once from _Glyceria
  aquatica_, to say nothing of its softer and smoother texture and
  small stature. _Poa trivialis_ may have two flowers, but it is
  an erect meadow-grass, with keeled and pointed glumes and paleæ.
  _Aira_ and _Agrostis_ are awned, or differ entirely in habit.

          †† Spikelets with at least three or four, but usually more
             flowers.

            ⊙ _A perennial field-grass with few large, compressed,
              bluntly triangular or ovate spikelets, dangling at the
              end of capillary branchlets; with membranous, loosely
              imbricated, concave and inflated paleæ and glumes,
              and 6-8 flowers._

              _Briza media_, L.

  The much rarer _B. minor_, L. is an annual and smaller.

            ⊙⊙ _Spikelets small and numerous, more or less elongated and
               pointed, not dangling: glumes and paleæ not inflated_.

  _Poa_ and _Festuca_ (see p. 116) are difficult genera for the
  beginner; several of the species vary considerably in detail.
  Generally speaking the spikelets of _Festuca_ are hard, harsh
  and sharply pointed, or with short or evident awns; in _Poa_
  they are softer, and with blunter points, and never awned. The
  most obviously awned species of _Festuca_ have more or less
  setaceous leaves and contracted inflorescences (see p. 111). Some
  of the mountain species of _Poa_ are extremely variable in small
  characters.

              ≡ _Reed-like aquatic, with obtuse glumes rounded dorsally;
                the large richly branched panicle bearing numerous 5-10
                flowered spikelets. Sheath entire or nearly so. No we
                to the paleæ._

                _Glyceria aquatica_, Sm.

  For other reed-grasses, see note, p. 103. _Glyceria fluitans_ has
  a more contracted panicle and usually more flowers in the spikelet
  &c. (see p. 111).

              ≡≡ _Meadow and pasture grasses &c., usually small. Glumes
                 more or less keeled and acute. Sheaths split_.

                 +Poa.+

                ‡ _Spikelets very small and containing 2-3 flowers only.
                  Stem slender, terete and rough; ligule long and acute,
                  palea with prominent lateral nerves._

                  _P. trivialis_, L.

  The flowers are fewer than in any other _Poa_, and may be only two.
  _P. nemoralis_, with 3-5 flowers, may also occasionally be found
  with two only: it differs from others in its more acute glumes,
  smooth stem and short ligule.

  _P. pratensis_ differs in its creeping stolons, short ligule and
  more numerous 4-5 flowers, and in the indistinct nerves of the
  palea.

                ‡‡ _Spikelets 4-6 flowered._

              ≡ _Annuals, about six inches high, with relatively
                large and numerous spikelets for so small a panicle.
                No “web” at the base of the paleæ._

                _P. annua_, L.

  This is the small grass so common as a weed on road-sides and on
  lawns, flowering even in winter. For other annual species of
  _Poa_--_P. rigida_, _P. loliacea_ and _P. procumbens_--see note p.
  108 and p. 111.

              ≡≡ _Perennials._

                Δ _With creeping stolons._

                  _x Stems and leaf-sheaths flattened. Panicle somewhat
                     close and secund, some spikelets being nearly
                     sessile._

                     _P. compressa_, L.

                  _xx  Stems and leaf-sheaths terete. Panicle spreading
                       widely._

                       _P. pratensis_, L.

                ΔΔ _Without creeping stolons. Stems and panicle slender,
                   round. A shade-plant._

                   _P. nemoralis_, L.

  The rarer species of _Poa_ are _P. bulbosa_ with the stems swollen
  below; _P. alpina_, also slightly bulbous and often viviparous; _P.
  laxa_ an allied Highland species; and _P. distans_ a maritime form
  allied to _P. maritima_ (see p. 111).

        ** Spikelets with awns or with sharp terminal points (awn-points)
           to the glumes or paleæ.

  In some species and varieties of _Festuca_ awns are not evident
  (see p. 116): the hard paleæ simply end in acute or acuminate
  points, but these are sharp and in most cases much more so than in
  any _Poa_. When not so evident, the student will probably think the
  specimen is a _Poa_ and the flora must be consulted.

  The difficulty is most likely to occur with varieties of _F. ovina_
  and _F. elatior_: in the former the leaves are narrower, setaceous
  and stiffer than in any _Poa_. The ribbing of the leaf, the ligule,
  and other characters of the vegetative organs (see pp. 45 and 50)
  will help in these doubtful cases.

          † Awns terminal, or sub-terminal; often very short or nearly
            obsolete and the paleæ merely drawn out at the tips to a
            hard sharp awn-point.

            ⊙ _Awns long and sub-terminal, inserted between the teeth
              of the cleft apex of the paleæ. Sheaths entire. Panicle
              usually nodding._

              +Bromus.+

  With the exception of _Festuca Myurus_ and one or two other rare
  Fescues with setaceous leaves, _Hordeum_ and _Brachypodium_ are
  the only other genera with awns much resembling the Bromes. The
  former has a totally different inflorescence, and in the latter the
  spikelets are practically sessile (see p. 107).

              ≡ _Spikelets short and fat, and relatively heavy. Paleæ
                broad and distinctly nerved. Awns fine, about as long
                as the paleæ._

                _B. arvensis_, L.

There are several varieties, of which _B. secalinus_ with a looser
panicle, and _B. mollis_ with a more compact panicle and very downy,
are the chief.

              ≡≡ _Spikelets lanceolate and with conspicuous awns.
                 Nerves on the paleæ obsolete._

                _x Panicle conspicuously loose and drooping and awns
                   long, paleæ narrow and elongated._

                  _z Sheaths with long often reflexed hairs.
                     A shade-grass over three feet high._

                      _B. asper_, Mull.


                  _zz Sheaths downy. A weed of open lands and hedges,
                      two feet or less._

                       _B. sterilis_, L.

  _B. giganteus_ is rarer than _B. asper_ and has smaller spikelets
  and more slender awns. _B. maximus_ and _B. madritensis_ are rare.

            ⊙⊙ _Awns, if present, merely the points of the paleæ,
               very short or obsolete. Sheaths split: ligule short._

               +Festuca.+

              ≡ _Leaves flattened. Panicle somewhat close. Often tall
                grasses._

                _z Meadow-grass, with 5-6 to a dozen or more flowers
                   in the spikelet._

                   _F. elatior_, L.

                _zz Shade-grass, with 4-5 flowers only in the
                    spikelet._

                     _F. sylvatica_, Vill.

              ≡≡ _Leaves subulate or setaceous, at least below. Mountain
                 pasture grass, usually small._

                 _F. ovina._

  Concerning difficulties between _Poa_ and the awnless forms
  of _Festuca_, see p. 114. _F. elatior_ and _F. sylvatica_ are
  practically awnless, the awn-points being merely the acuminate tips
  of the paleæ.

  The long-awned species of _Festuca_ have compact stiff panicles and
  narrow or setaceous leaves (see p. 111).

  Regarding varieties of _F. ovina_, see p. 112.

          †† Awns, twisted below and bent above, inserted into the
             middle of the back of the bifid palea or below it.

            ⊙ _Awns long and conspicuously projecting from the spikelet,
              which is gaping and contains 3-5 flowers. Leaves flat._

              +Avena.+

              ≡ _Tall annual corn-weed, with large (18-20 mm.) heavy,
                pendent, hairy spikelets on the long slender stalks
                of the lax open panicle. Leaves glabrous._

                _A. fatua_, L.

  This is the so-called Wild Oat, and the type of this group.

              ≡≡ _Tufted perennials with spikelets more or less erect on
                 stiffer stalks, the panicle therefore less open._

                _z Panicle nearly simple; spikelets silvery or
                   reddish, 12-15 mm. long._

                   _A. pratensis_, L.

                _zz Panicle branched but not very open; spikelets
                    glistening yellow and only 5-6 mm. long._

                    _A. flavescens_, L.

  There is no other genus closely resembling _Avena_. The superficial
  likeness of some Bromes disappears at once on examination. The
  spikelets of _Aira_ are much smaller, and the leaves quite
  different (see below and p. 47).

            ⊙⊙ _Awns fine and hair-like and not conspicuously protruding
               from the spikelets; the latter small, 2-5 mm. Flowers two
               in each spikelet._

               +Aira.+

              ≡ _Coarse and tall tufted grass with flattened, harsh, and
                conspicuously ribbed leaves: the very short awns hardly
                protruding._

                _A. cæspitosa_, L.

  No other grass can be confused with this if the very high ridges of
  the leaves are observed (see p. 47).

              ≡≡ _Small grasses with setaceous or very narrow inrolled
                 leaves. Awns slightly protruding._

                _x Palea distinctly bifid at the apex: awn nearly
                   twice its length. A very small grass about six
                   inches high: leaves subulate, fine and short._

                   _A. caryophyllea_, L.

                _xx Paleæ almost imperceptibly bidentate: awn not much
                    longer than palea. About 12-18 inches high: leaves
                    inrolled._

                    _A. flexuosa_, L.

  Other species of _Aira_, with more condensed inflorescences, are
  dealt with on p. 112. _Agrostis_ is distinguished by the leaves and
  one-flowered spikelets (see p. 104). _Poa_ and _Catabrosa_ have no
  awns.




CHAPTER VIII.

THE FRUIT AND SEED.


The stigma of an ordinary grass consists of two divaricating plume-like
structures composed of thin-walled cells. When the paleæ open these
stigmatic plumes protrude, one on either side, and readily catch pollen
shed from the dangling stamens and carried by the wind, and since the
pollen of the same flower is usually shed at a time when the stigmas
of many neighbouring plants are mature, there is every opportunity for
cross-fertilisation. (Fig. 33.)

In some cases, however, e.g. _Anthoxanthum_, _Alopecurus_, the flowers
are proterogynous, the stigmatic plumes being ready for pollination
some time before the pollen is shed from the anthers of the same
flower; whereas in most of our grasses the pollen begins to scatter
before the stigmas are ready (protandrous). Among exotic grasses, many
are diœcious or monœcious--i.e. the flowers contain stamens
only or ovary only, on each plant, or on different inflorescences
of the same plant respectively--and even in our own _Holcus_ and
_Arrhenatherum_ this state of affairs is partially represented, since
one flower of the spikelet is male only.

In some grasses, e.g. Rye, however, it appears improbable that
cross-fertilisation ever occurs, since the paleæ do not open, and the
pollen falls on to the stigma direct; and in _Leersia_ and the foreign
_Amphicarpum_ the spikelets are completely cleistogamous, those of the
latter being on stalks close to the ground which push the flowers into
the soil, where pollination and fructification are accomplished.

Hybrid grasses are by no means uncommon. To say nothing of the numerous
cross-bred Wheats and Barleys, artificial hybrids have been raised
between Wheat and Rye. In the Maize an astonishing number of selected
cross-breeds have been obtained, and, among others, certain forms in
which the seeds have a violet outer layer and a sugary endosperm, are
found to transmit these characters to the resulting seed of a variety
which would normally have produced seed with white outer layers and
starchy endosperm, if the pollen of the former is used on the stigma of
the latter. Such direct influences of the pollen are termed _Xenia_.

[Illustration: Fig. 37. Pollen-grains adherent to the papillæ of the
stigma, on which they germinate, sending the pollen-tubes down between
the cells. Kerner. × about 100.]

When the pollen-grain, having adhered to the hairy stigma, has begun
to germinate, the resulting pollen-tube creeps down between the cells
of the stigma, and hands over its enclosed nuclei to the embryo-sac,
where fertilisation of the egg-cell is accomplished, by the fusion
of one of the pollen nuclei with the nucleus of the egg-cell. As the
resulting embryo developes, the sac becomes filled with endosperm-cells
charged with starch-grains or sugar, and in the ripe seed the embryo is
always found affixed laterally and below to this endosperm--a point of
distinction from Sedges, where the embryo is buried in the endosperm.

The ripe seed fills the ovary, and its outer walls usually fuse with
those of the carpel, forming the well-known _Caryopsis_ or “grain.”

[Illustration: Fig. 38. Longitudinal median section of the caryopsis
of a grass--e.g. _Lolium_ (× about 35). _p_, pericarp; _t_, attachment
to axis; _m_, position of micropyle; _E_, endosperm; _A_, its aleurone
layer; _l_, folded leaves of plumule; _r_, radicle; _r´´_, secondary
roots; _RC_, root-cap; _s_, scutellum. The dark line _e_ represents the
surface where the face of the scutellum is applied to the endosperm and
where absorption of the latter takes place.]

If such a “grain” is carefully examined, three chief parts are visible
in addition to the embryo. (Fig. 38.) Firstly, we find on the outside
the fused seed- and fruitcoats, differing in the number of layers and
in the microscopic characters of the cells, some of which characters
can be employed in diagnoses. (Fig. 39.)

Secondly, the great mass of the “grain” internally is composed
of delicate cells filled in most cases with starch-grains, the
sizes, shapes and arrangement of which can also be employed for
diagnoses--e.g. the compound grains of the Aveneæ and Festuceæ
are different from the simple polyhedral or rounded grains of the
Andropogoneæ and Maydeæ, and some races of Maize have sugar and soluble
starch instead of grains of the latter.

[Illustration: Fig. 39. Transverse section (highly magnified) through a
grain of _Brachypodium pinnatum_ taken about half-way up. 1, epidermis;
2, pericarp; 3, remains of the true seed-coat; 4, vascular bundle; 5,
remains of nucellus; _P_, epidermis of nucellus; _G_, aleurone layer:
remarkable in being several cells thick; _E_, endosperm. Harz.]

Thirdly, the outermost layer or layers of cells of the endosperm are
filled with proteids, and are known as the Aleurone layer. (Fig. 38,
_A_.)

The embryo consists of the folded embryonic leaves in bud (plumule)
above, which will grow up on germination as the shoot or “spear,” the
short primary root (radicle) below, with in many cases two or more
secondary rootlets already showing in its tissues, and from the common
“collar” uniting these a more or less prominent shield-shaped organ
(scutellum) standing out laterally in contact with the endosperm, the
dissolved contents of which it absorbs on germination. (Fig. 38, _s_.)

Although typical grasses form a caryopsis as described, exceptions
occur. In the exotic _Sporobolus_, _Eleusine_, _Crypsis_ and
_Heleochloa_ the fruit becomes truly dehiscent, the seed being loose in
the fruit, and the latter opens and allows it to fall out; and in many
Bamboos the seed is loose in the _achene_, while in a few cases--e.g.
_Melocanna_--the fruit is fleshy and may be as big as a walnut.

Returning to the typical grasses. When the fruit ripens in the
spikelet, several events may happen.

[Illustration: Fig. 40. _Triodia decumbens. a_, “seed,” nat. size;
_b_, ditto, × 6. Note the basal hair-tuft and rachilla, and the
ciliate, toothed outer palea with a short awn-point, enclosing the
inner more delicate palea. Between the two lies the caryopsis. Nobbe.]

In most of our grasses the caryopsis comes away trapped between its
two paleæ, and the latter bring away with them the small piece of
the axis of the spikelet on which they stand: this bit of axis--the
_rachilla_--often affords valuable characters in diagnosis. (Fig. 41.)
It is the pair of paleæ enclosing their caryopsis which goes by the
name of “seed” in most of our grasses. (Fig. 40.)

In a few cases, however, e.g. _Panicum_, the spikelet comes away as a
whole, so that here the “seed” consists of the glumes, enclosing one,
two or more pairs of paleæ with their contained caryopses.

Even among our native grasses, however, cases occur where the
separation takes place below some of the glumes, and so the “seed,” as
met with in samples, consists of glumes as well as enclosed paleæ and
caryopsis--e.g. _Anthoxanthum_, _Alopecurus_, &c.--and some care is
necessary in examining grass “seed” in these circumstances (see p. 134).

[Illustration: Fig. 41. Diagram of a spikelet of a grass--e.g.
_Festuca_--comprising six matured flowers and their paleæ, embraced
by the two glumes (_g^1g^2_) at the moment of disarticulation as the
fruits ripen. The small piece of axis (_a_) left attached to each
segment is the rachilla _R_. At _p^2_ the tip of the inner palea is
visible protruding from the outer one _p^1_: in the rest it is still
enclosed in the latter.]

Interesting biological adaptations are met with in the distribution
of grass “seeds.” The very small and light fruits of _Agrostis_
easily fall and are scattered by the wind, but in many cases the
glumes (_Holcus_) or paleæ (_Briza_) are expanded and serve as “wings”
offering extensive surfaces to the wind. In _Arundo_, _Calamagrostis_,
_Aira_, &c., fine silky hairs attached to the rachilla serve a similar
function, reminding us of the _coma_ of true seeds and the _pappus_ of
Composites. In _Hordeum jubatum_ of the prairies, the axis breaks up
and the disarticulated portions with their attached tufts of fruits
are blown away by the wind, and something similar occurs in our own
_H. murinum_ to a less extent. In the exotic _Spinifex_ whole heads of
fruits are thus detached and blown over the sands as “tumble weeds.”

In _Stipa pennata_ we have an example of perhaps the most complex of
all such adaptations: the exceedingly long awn terminating the palea
is plumose at the upper end and twisted below, and the hard sharp
rachilla at the base of the fruit is furnished with short, stiff hairs
directed upwards. The plumed awn serves as a wind surface, the whole
fruit flying like an arrow through the air. The stiff hairs below serve
to fix the lower end between particles of soil, and by their alternate
drying and wetting, the warping of these and of the twisting and
untwisting awn drives the sharp base into the soil. (Fig. 42.) Similar
mechanisms exist in _Avena_ and others.

These bristles and awns also subserve dissemination in other ways,
especially by clinging to the wool and fur of sheep and other animals,
and cases occur where the twisting awns and reflexed hairs on the hard
pointed fruit-base drive the latter into the bodies of sheep with fatal
effects--e.g. _Stipa capillata_ in Russia, _S. spartea_ in America,
_Aristida hygrometrica_ in New Zealand, _Heteropogon contortus_ in New
Caledonia.

[Illustration: Fig. 42. Awned fruit of _Stipa_. The reflexed stiff
hairs and hard point favour penetration into the soil. The long twisted
awn performs hygroscopic movements, and its terminal plume offers
surface to the wind. Lubbock.]

The driving action of even small reflexed asperities on awns is well
illustrated by the fruits of _Hordeum_, which are often made by
children to creep up the sleeve.

When we come to examine the external features of the “seeds” of
grasses--usually the caryopsis enclosed in one or more paleæ, but
sometimes in glumes as well--the following diagnostic characters are of
importance.

The size varies from lengths of 2 mm. or less (_Poa_, _Aira_)
(Figs. 43, 44) to 15-20 mm. or more (_Arrhenatherum_) (Fig. 47)
and distinction must be made between the various characters of the
caryopsis devoid of its coverings (paleæ, glumes) and such as really
belong to the latter.

The caryopsis proper may be short and stout and devoid of a
groove--“Millet-seed” type (Fig. 45)--but is oftener elongated, like a
grain of Wheat, and then has the characteristic longitudinal groove on
the face opposite that where the embryo is situated (Fig. 46). Details
of shape--e.g. cylindroid, fusiform, flattened, &c.--are also of
diagnostic value.

[Illustration: Fig. 43. _Poa annua. d_, the “seed,” nat. size; _a_
and _b_, ditto, × about 7; _c_, caryopsis, natural size (above) and
× about 7. Note the ribs and silky keel. No “web.” Nobbe. Cf. Figs.
54-56.]

In many cases the “seed,” consisting of the caryopsis closely
compressed between the paleæ, is boat-shaped, e.g. _Lolium perenne_,
_Festuca elatior_. If this “boat” is long and narrow it may be termed
barge-shaped, e.g. _Brachypodium sylvaticum_, &c. (Figs. 71, 72): if
short, broad, and open or shallow, the term coracle-shaped seems to
apply, e.g. _Bromus arvensis_ (Fig. 73).

[Illustration: Fig. 44. _Aira cæspitosa._ The minute “seed” (nat. size)
is seen to the right, and the caryopsis (nat. size) to the left of _c_,
the caryopsis, × 8. _a_ and _b_, the “seed,” × 10. The basal awn is
about as long as the palea, and the rachilla is very hairy. Nobbe.]

[Illustration: Fig. 45. _Phleum pratense._ Millet-seed type. _a_,
“seed,” nat. size; _b_, ditto, × about 7; _d_, caryopsis, nat. size;
_c_, ditto, × 7. The rounded caryopsis in _b_ is only loosely covered
by one palea. Nobbe.]

[Illustration: Fig. 46. Boat-shaped “seed” of _Glyceria fluitans_. _a_,
nat. size; _b_ and _c_, × about 6. _d_, caryopsis, × about 10. Note the
5-7 strong nerves, and the slender cylindrical rachilla. Cf. Figs. 57
and 58. Nobbe.]

[Illustration: Fig. 47. _Arrhenatherum avenaceum._ The “double seed”
(_a_ and _b_) consists of two pairs of paleæ with their enclosures. The
lower pair (γ) are devoid of fruit, and the outer palea has a long
twisted and kneed basal awn: the upper pair (β) enclose the fruit,
and the palea has a short straight awn. Note the stiff basal hairs.
_a_, nat. size; _b_, × about 6; _c_, caryopsis, nat. size; _d_, ditto,
× 6. Nobbe.]

[Illustration: Fig. 48. _Lolium temulentum._ Type of boat-shaped “seed”
with sub-terminal awn arising from between two teeth. _c_, “seed,” nat.
size; _a_ and _b_, ditto, × 6. Note the large smooth rachilla. Nobbe.
Cf. Fig. 57.]

Further important distinctive characters are obtained from the absence
or presence of awns, and the peculiarities--length, stiffness, &c.--of
the latter. The awns may be straight, hooked, or kneed (i.e. sharply
bent); twisted or not; smooth or serrulate. They may be inserted at the
base or near the middle of the back of the investing palea, or glume,
or near its apex, as indicated by the terms basal, dorsal, sub-terminal
(see Figs. 47-50).

Some difficulty arises in connection with terminal awns. In some
cases there is a true awn--i.e. a distinct bristle or hair--at the
apex of the palea, and apparently continuing its substance without
interruption; but in most instances close examination shows that this
awn arises from between two minute teeth, and is really inserted at the
back of the slight depression between them--e.g. _Lolium temulentum_
(Fig. 48), _Brachypodium pinnatum_ (Fig. 77), &c.

In another class of cases the awn appears to be really the prolongation
of the palea--e.g. _Nardus_ (Fig. 81), _Festuca Myurus_ (Fig. 80),
&c.--and when it runs out into a distinct bristle we may speak of a
terminal awn without staying to discuss whether or no it is really
terminal in development.

[Illustration: Fig. 49. _Agrostis Spicaventi. c_, “seed,” nat.
size; _a_ and _b_, ditto, × about 9. The long slender awn is inserted
below the bifid tip of the palea. Nobbe.]

In _Arundo_, _Cynosurus_ and some Fescues, where the palea tapers off
into a stiff long point, I have not spoken of it as an awn, but have
described the palea as tapering into a sharp point (awn-point). It
must be admitted that the distinction is somewhat artificial, but it
has its advantages in practice.

[Illustration: Fig. 50. _Bromus sterilis. a_, “seed,” nat. size; _b_
and _c_, ditto, × about 2. Nobbe. Cf. Figs. 80 and 81.]

[Illustration: Fig. 51. _Festuca sylvatica. a_, “seed,” nat. size;
_b_ and _c_, ditto, × 8. Nobbe. Cf. Fig. 78.]

The rachilla (Fig. 41), when present, often affords good characters,
and in a few cases is relied on for the distinction of “seeds”
otherwise much alike--e.g. _Lolium perenne_ and _Festuca elatior_; and
similarly with the presence or absence of hairs (_Digraphis_, _Arundo_,
&c.) or “web” (_Poa_) at the base of the “seed.” (Figs. 55, 69.)

On germination the primary root of the embryo usually emerges and
at once plunges into the soil, but soon ceases to grow, and the
secondary roots (and subsequently adventitious rootlets from the lower
internodes) soon give the peculiar fibrous character so well known in
grass-roots.

The plumule either pushes out from the same end of the caryopsis as
the root (e.g. Wheat, Rye) or drives its way between the coats to the
opposite end (e.g. Barley) and appears as a pointed cylinder of rolled
leaves (the “spear”) the outermost of which is sheath only, no lamina
being developed. As Darwin showed, the pointed apex of such a plumule
is hardened, facilitating the piercing of the soil above, and when the
blade attains the open air it performs spiral movements during growth,
indicating that similar attempts to rock from side to side have aided
the plumule in forcing its way through the soil. It has also been shown
that the apices of roots and plumules are sensitive to differences of
temperature, of light-intensity, moisture and contact, all of which aid
the seedling in establishing its position in the soil and in liberating
the “spear.” For particulars the student should read Darwin’s _Power of
Movement in Plants_.

With regard to the established seedlings of grasses, many interesting
details of structure are to be found in them. I have not sufficient
material to draw up a diagnostic arrangement of grass-seedlings, but it
is evident that such could be done. It may be useful to illustrate this
by the following tabular view of the characters of the larger seedlings
of our common cereals, in part adapted from Vesque and Percival; though
I find that some variations may occur, especially in the development of
the auricles.


SEEDLINGS.

  I. First expanded aerial leaves broad, bright green, with 18-24 ribs.

     _Barley._

  The blade tends to twist to the left: auricles, when well developed,
  long, pointed, and claw-like, embracing the glabrous sheath in
  front. Ligule long, membranous, pointed and irregularly toothed. The
  plumule emerges at the upper end of the grain, and the embryo has 5-6
  secondary roots.

  II. First aerial leaves narrower, with not more than 11-13 ribs.

      A. _Ligule long, rounded and toothed._

         _Wheat._

  The blade tends to twist to the left: auricles filiform and embrace
  the densely pubescent sheath. Leaves green. Embryo with three roots.

      B. _Ligule short and toothed. Leaves with a reddish cast._

        (_a_) Blade and sheath softly hairy, the latter with scattered
              long hairs, the former tending to twist to the left.

               _Rye._

  The first leaf-sheath purple. Auricle-claws more triangular and
  smaller than those of wheat, and the accompanying bristles are fewer
  and shorter. Embryonic roots four.

        (_b_) Blade and sheath glabrous or merely ciliate or silky, the
              former tending to twist to the right.

              _Oat._

  Auricles filiform. The plumule emerges above. The embryo has three
  roots.

A curious phenomenon is observed in some grasses growing in high
latitudes, or mountainous regions, or in moist situations. The
flowers, or even entire spikelets, grow out into minute leafy buds,
with rudimentary roots at the base, and fall off like the bulbils
of other monocotyledons, taking root directly in the damp soil.
The phenomenon must be looked upon as a case of apogamy, since the
development of sexual organs is entirely passed over; the parts which
would normally have become ovary and stamens being transformed into
leaves. In some species or varieties--e.g. _Poa alpina_, _Festuca
ovina_--this viviparous condition may coexist with normal flowers
and spikelets; in others--e.g. _Poa laxa_, var. _stricta_--only the
viviparous state occurs.

In the following arrangement the student should note that the terms
“Seed” and “Fruit” are used in the ordinary sense of the farmer and
seedsman: by the former is meant the “seed” as it comes in samples
into the market, when the true fruit or grain (_Caryopsis_) is almost
invariably invested by adherent “chaff”--i.e. paleæ or glumes or
both. When the word Caryopsis is employed, I mean it strictly in the
botanical sense explained above. In _Hordeum_, for example, we never
see the true fruit, the grain consisting of the caryopsis with paleæ
so closely adherent to it, that we are apt to take them as part of
the grain itself. The true seed, in the strict botanical sense, is
never seen as a naturally separate organ in our native grasses; and,
as already explained, only very few exotic grasses ever shed it--e.g.
_Sporobolus_.




CHAPTER IX.

CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS).


  +I. “Seed” rounded (Millet-seed[12] type). Caryopsis ovoid or
  sub-globose, devoid of distinct groove, and distending the awnless
  paleæ, or falling out free.+

    +A. Glumes cuspidate, “fruit” yellowish.+

    _Phleum pratense._

The student should familiarise himself with the “seed” of _Phleum
pratense_, as a type, and an important grass easily obtained pure, but
sometimes with minute round seeds of weeds intermixed.

_Phleum pratense_, L. (Fig. 45).

Palea 2·3 mm. long, five-ribbed, with a short point, delicate but hard,
smooth, with a silvery lustre. Inner pale two-nerved. Closely investing
the yellow-brown caryopsis, which easily falls out and is ovoid-acute,
about 2 mm. long by 1 broad, and finely punctate.

  The much rarer _P. arenarium_ and the very rare _P. Bœhmeri_ and
  _P. asperum_ also come here.

  _Phleum_ is not easily confounded with any other of our grasses,
  and _Briza_ and _Glyceria_ are almost the only other common grasses
  of about the same size of which the caryopsis often falls free from
  the palea (“naked fruits”). _Glyceria_ is longer and corn-shaped,
  and _Briza_ usually larger. _Anthoxanthum_ and _Phalaris_ are easily
  distinguished. _Agrostis_ is smaller and “corn-shaped.” Certain
  species of _Panicum_ present resemblances, but the enveloping paleæ,
  &c. are very different. _Melica_ also occurs as “naked fruits,” but
  is rarely seen, and its colour and brilliant lustre distinguish it.

    +B. Glumes not cuspidate. “Fruit” not yellow.+

      (_a_) “Fruit” white, owing to the closely investing palea.

             _Milium effusum._

  A common grass, but not often met with in “seed” grasses. It is
  eagerly eaten by birds.

  _Milium effusum_, L. (Fig. 52).

Palea about 3 mm. long, with few nerves, closely investing the
caryopsis: the seed is ellipsoid-acute, slightly compressed, and
2·2-2·7 mm. long. The inner pale becomes hard and shines like porcelain.

      (_b_) “Fruit” dark-brown shining; slightly flattened and grooved.

            +Melica.+

[Illustration: Fig. 52. _Milium effusum._ “Seed,” _a_, nat. size; _b_
and _c,_ × 7. Nobbe.]

  _Melica_ is rarely met with as “seed.” When it is, it has to be
  distinguished from the other “Millet-seed” types which readily fall
  as naked fruits--see _Phleum_, _Milium_, &c. _Agrostis_, _Glyceria_
  and other corn-shaped “seeds” are easily distinguished.

  _Melica nutans_, L. (Fig. 53).

“Seed” coracle-shaped. Palea broad, parchment-like, elliptic convex,
5-6 mm. long, 5-7 nerved and keeled, awnless, loose, purplish.
Caryopsis ellipsoid-acute, 2-3 mm. long, and easily separating,
wrinkled, dark shining brown as if lacquered.

[Illustration: Fig. 53. Coracle-shaped “seed” of _Melica nutans_,
showing the broad, ribbed and keeled palea (_c_), and small rachilla
(_d_). _a_, the “seed,” nat. size; _c_ and _d_, ditto, × 8; _b_, the
caryopsis, nat. size; _e_ and _f_, ditto, × 10. Nobbe.]

  _M. uniflora_, Retz. is commoner and very similar, but neither is
  often met with in “seed” grass, except as impurities among Fescues.

  The rare _Panicum Crus-galli_ and allies, and the rice-like _Leersia
  oryzoides_ as well as _Cynodon Dactylon_, come here.

  Panicums may occur in grass “seed” from America: Burchard describes
  them in detail.

  +II. “Seed” long (Corn and Barley type). Caryopsis oblong or
       flattened, usually trapped between the boat-shaped paleæ: if
       otherwise, with an awn.+

    +A. “Seed” awnless. There may be a short sharp point to the palea
        (mucronate), but no prominent hair-or bristle-awn exceeding half
        the length of the palea.+

      (_a_) A “web” or tuft of hairs at the base or on the rachilla.

        (1) _Hairs of basal tuft silky and erect._

          * Pencil of hairs as long as palea or longer.

_Calamagrostis lanceolata_, Roth.

Palea 3 mm. long, thin, two-toothed and with a short bristle at the
apex.

  Other species of _Calamagrostis_ are awned. None occurs as an
  ordinary impurity in “seed.”

_Arundo Phragmites_, L.

Palea narrow and long, 10-11 mm., delicate, entire, tapering to an
acuminate point, violet, three-nerved, smooth. Caryopsis about 2 mm. A
pencil of long silky hairs on the rachilla.

  The long acuminate point is almost an awn.

  _Calamagrostis_ also has long basal hairs: both are useless grasses
  agriculturally. For _Glyceria_ see note, p. 146. _Avena_, _Aira_ and
  _Psamma_ are easily distinguished.

          ** Pencil of hairs short.

            † _Palea mucronate, 11-12 mm. long: caryopsis 4·5 mm._

              _Psamma arenaria._

  _Digraphis_ differs in the stout caryopsis, smaller size, double
  hair-tuft. _Arundo_ has a long pointed palea and long silky basal
  hairs and is larger.

_Psamma arenaria_, Beauv.

Palea 11·5 mm. ovate-lanceolate, papery, 4-5 nerved, as rolled round
the fruit about 1·3 mm. diameter, yellow, and with a small tuft of
stiff fine hairs at the base. Mere trace of awn, sub-terminal. Fruit
4-5 mm. long, obovate, pale-brown.

  A shore-grass, not often seen as “seed”: more valuable as a
  sand-binder than as fodder, though the young shoots are grazed.

            †† _Palea acuminate, and only about 4 mm. long: caryopsis
               1·4 mm._

               _Digraphis arundinacea._

  A Fen-grass, but coarse and not in use except the young growth, and
  for thatching.

_Digraphis arundinacea_, Trin.

Paleæ ovate-lanceolate, nerveless and awnless, but silky with double
basal hair-tuft, and polished at the base; smooth, hard and shining,
and closely investing the caryopsis which has no groove. Dark grey in
colour. The glumes are without awns or wings, and are left behind.

  The allied _Phalaris canariensis_ has wing-like keels to the glumes.

  _Triodia_ also comes into this group, with short basal hairs; but its
  broad ciliate palea, 6 mm. long, has a short mucronate point between
  two teeth (Fig. 40).

        (2) _Hairs at the base forming a fluffy “web.” Paleæ thin,
            2-3 mm. long._

            _Poa pratensis._
            _P. trivialis._
            _P. compressa._
            _P. nemoralis._

  The “seeds” of _Poa_ proper are nearly all small--not more than 3-4
  mm., more or less lanceolate, with tough, keeled glumes, and when
  “webbed” tend to adhere together as if stuck with cobweb. The keeled
  glumes give them an angular appearance--triangular in section--and
  make them tend to lie on the side. Rachilla evident. Nerves of paleæ
  distinct.

_Poa pratensis_, L. (Fig. 55).

“Seed” 2-3 mm. long, brownish: caryopsis about 1-1·5 mm. Outer
palea acute, indistinctly 3-5 nerved, edges and keel, silky; margins
overlapping the hyaline inner palea.

The “web” looks like hyphæ of a mould.

Caryopsis ellipsoid-acute, with traces of the stigma. It falls easily.
No distinct groove, section somewhat triangular. Rachilla truncate.

[Illustration: Fig. 54. _Poa nemoralis. c_, the minute “seed” (to
the right) and caryopsis (to the left) nat. size. _a_, the “seed,” ×
8; _b_, the caryopsis, × 8. Traces of a basal “web,” not shown here,
occasionally occur. Nobbe.]

[Illustration: Fig. 55. _Poa pratensis._ Type of a “webbed seed.” _a_,
“seed,” × about 7; _b_, caryopsis (inverted), × 7. Between are the
same, nat. size. Note the nerves on the palea and the conspicuous “web”
at the base _a_. Nobbe.]

[Illustration: Fig. 56. _Poa trivialis. a_, “seed,” nat. size and
× 8; _b_, caryopsis, nat. size and × 7. Note the conspicuous “web.”
Nobbe. Cf. Fig. 43.]

_Poa compressa_, L.

Palea obtuse, nearly glabrous and nerveless, or faintly 3-5 nerved and
with a faint web. It is close to _P. pratensis_.

_Poa trivialis_, L. (Fig. 56).

“Seed” 2-2·5 mm., and with a bluish or bronzed cast. Caryopsis 1-1·5 mm.

Palea acute, distinctly five-ribbed, glabrous, the margin scarcely
overlapping. Caryopsis grooved, blunt and more tightly held in the
palea.

  _P. trivialis_ differs from _P. pratensis_ chiefly in the distinct
  ribs and smoother palea, grooved caryopsis, and bluer hue.

_P. nemoralis_, L., hardly differs from _P. trivialis_, but the paleæ
are sub-acute, nerves obsolete, and scarcely hyaline at the margins.
The “seed” is shorter and more acute, and the colour less pronounced,
and with hardly a trace of hairs (Fig. 54).

When the basal hairs are absent this should go with _P. annua_, &c.
(see p. 146).

  It is practically impossible to distinguish these species by the
  “seed.” Care is necessary to distinguish _Kœleria_, which is
  somewhat larger in size, keeled, compressed and nerved similarly,
  but is more pointed and curved and paler yellowish white in colour.
  Hard and devoid of web or hairs. _Aira_ is distinguished by the awn:
  _Agrostis_ by the very different paleæ and caryopsis.

  The other Poas are devoid of web, though they may have hairs below,
  and require very careful examination. The whole group is excessively
  difficult to deal with in “seed,” and a special study of it is
  needed, since several species are important, and it forms a type.

      _b_ No web or pencil of hairs below the “seed.”

        (1) _Apex of palea rounded, blunt, notched, or at most bluntly
            pointed, but with no trace of awn-or bristle-tip._

          * Palea inflated, round-backed and somewhat winged,
            membranous.

            _Briza media._
            _B. minor._

_Briza media_, L.

Paleæ blunt, 2·5-3 mm., without lateral projections, markedly
convex--almost conduplicate; nerves several. Caryopsis ovoid, 1·5-2·5
mm., dark brown.

  Sometimes called a good grass, but meagre and only found in poor
  meadows in this country.

  It should perhaps go with the “Millet-seed” type and should be
  compared with _Phleum_, _Melica_, _Panicum_, &c. “Seed” seldom met
  with.

  _B. minor_ is smaller.

          ** Paleæ not inflated or winged.

            † _Paleæ broad, flat and truncate, prominently three-ribbed.
              Caryopsis 2 mm. long._

              _Catabrosa aquatica_, Beauv.

  Cattle like it, but it only grows in ditches &c. in water-meadows:
  distinction from _Glyceria aquatica_ easy if the paleæ are examined.

            †† _Paleæ acute or sub-acute, boat-shaped._

              ⊙ _Paleæ and “seed” at least 6-8 mm. long._

                ≡ _Rachilla flattened or angular, and tapering below._

                  _Lolium perenne._

  Occasionally awned, and then less easily distinguished from _L.
  temulentum_. One of our most valuable grasses. It forms a distinct
  type of boat-shaped “seeds.”

_Lolium perenne_, L. (Fig. 57).

Palea distinctly five-ribbed, glabrous, oblong-lanceolate, obtuse or
sub-acute, awnless, about 7 mm. long. Margins membranous. Inner palea
nearly as long, delicate, ciliate.

Rachilla short, flattened and angular, tapering below (see _Festuca
elatior_).

Caryopsis about 3·5 mm. long, obovate, yellowish brown.

[Illustration: Fig. 57. _Lolium perenne_ with typical boat-shaped
“seed.” _a_, natural size; _b_ and _c_, × about 8. _d_, caryopsis, × 8.
The rachilla, in _c_, is broader upwards and flatter than in Fig. 58.
Nobbe.]

[Illustration: Fig. 58. _Festuca elatior_, var. _pratensis_. Lettering
and sizes as in Fig. 57: compare the more cylindrical and slender
rachilla. Nobbe.]

  Although _Bromus mollis_, _Holcus lanatus_, &c. occur as impurities,
  they are easily distinguished: the real difficulties are with
  _Festuca elatior_ and _F. pratensis_.

                ≡≡ _Rachilla cylindrical._

                   _Festuca elatior._

  This is an important grass, and should be thoroughly mastered as a
  type of the boat-shaped “seed.”

  This, with _Lolium_, _Agropyrum_, other Fescues, and even some Bromes
  and Poas, will give trouble until the student thoroughly masters
  the importance of the minute characters of size, nervature, of the
  rachilla, awn, palea, &c.

_Festuca elatior_, L. (var. _pratensis_) (Fig. 58).

Palea ovate-lanceolate, five-nerved, slightly scabrid, with a slight
membranous margin and cilia, rounded back, and no awn. 6-7·5 mm. long.

Caryopsis oblong-obovate, somewhat flattened, hardly grooved and
adhering to the paleæ, about 3-3·5 mm. long.

Rachilla cylindrical, smooth.

  The other varieties of _F. elatior_ cannot be distinguished by the
  “seed” alone: in my samples _F. elatior_ proper is longer than
  _F. pratensis_, and both have occasionally a trace of awn. Var.
  _arundinacea_ has a more acuminate, stiff point. _Festuca pratensis_
  has its palea as a rule somewhat more acute than _Lolium perenne_,
  and the flatter tapering rachilla of the latter is more closely
  appressed to the palea. The caryopsis of _Festuca_ also tends to
  adhere to the paleæ.

              ⊙⊙ _Paleæ and “seed” at most 3-3·5 mm. long._

                ≡ _Palea devoid of hairs or keel, notched or blunt,
                  and with no trace of awn._

                  Δ _Palea hyaline, nerves indistinct. Tips notched
                    or blunt._

                    _Agrostis alba._

  There is occasionally a very short basal hair (awn).

  _Agrostis_ and _Aira_ will present difficulties to the beginner, not
  only on account of their small sizes, but also from the variability
  as regards awns, basal hair-tuft, &c. None are of value, and most of
  them are weeds.

_Agrostis alba_, L. (var. _stolonifera_).

Palea enclosing the fruit 1·8-2 mm. long, white, delicate, membranous,
with a blunt notched apex and three (or five) nerves: occasionally
there is a fine kneed basal awn, not projecting.

The glumes may remain attached: the outer has a serrulate keel, and
often a violet hue. No awn. About 2-3 mm.

Caryopsis about 1·1 mm. long, oblong, yellow, corn-shaped, furrowed,
shining through.

_A. vulgaris_, L., is a variety with slightly smaller fruits, no awn,
and usually three nerves to the palea, but they cannot be distinguished
with certainty by the “seed.” Rachilla obsolete.

  The colour of the glumes may vary considerably and is sometimes
  yellow.

  The absence of awn, rachilla, and basal hairs distinguishes
  _Agrostis_ from _Aira_.

                  ΔΔ _Palea membranous, ribbed, tips scarious._

                     _Glyceria aquatica._
                     _G. fluitans._

_Glyceria aquatica_, Sm.

Palea strongly 5-7 ribbed, obtuse and scarious, about 4 mm. long. Green
with a purple cast. Caryopsis dark-brown, about 2 mm. long.

Inner palea punctate. Rachilla slender and cylindrical.

_Glyceria fluitans_, Br., is very similar, but longer (6 mm.) and more
slender; the palea scabrid with truncate or ragged tips, and the inner
palea not punctate. Yellow. (Fig. 46.)

  _Glyceria aquatica_ and _G. fluitans_ are sweet grasses of value in
  water-meadows only. The “seed” is not often met with.

  Not only with the Poas, but also with _Catabrosa_ are there
  difficulties in determination. _Molinia_ and _Kœleria_ also
  present difficulties with _Glyceria_: the former has fewer and
  feebler nerves. _Digraphis_ and _Arundo_ are easily distinguished by
  the basal hairs.

                ≡≡ _Palea acute and somewhat compressed and keeled,
                   and with hairs on the ribs. Tips nerved._

                   _Poa annua._
                   _P. maritima._
                   _P. distans._
                   _P. rigida._
                   _P. loliacea._
                   _P. bulbosa._
                   _P. alpina._

  Their “seeds” are all small, about 2-3·5 mm. only, and angular,
  brown, and present many difficulties (see note, p. 141).

_Poa annua_, L. (Fig. 43).

Palea 3·5 and caryopsis 2 mm. long, so that the “seed” is much larger
than _P. trivialis_, and there is no web. Minutely silky-hairy on the
keel, and the ribs are strong for a _Poa_.

_Poa alpina_, L., has the palea five-ribbed with stiffish hairs below,
but no web. Bronzy green-violet. “Seed” 3-3·5 mm. long. Caryopsis 1·5-2
mm., and slightly grooved. It is rare in England, and is interesting as
it becomes viviparous in Alpine situations.

        (2) _Apex of palea distinctly pointed, acuminate or mucronate,
            but not giving rise to a true, long, bristle-like awn._

          * Palea acuminate--i.e. taper pointed.

            † Not compressed or obviously keeled.

              _Festuca ovina._
              _F. sylvatica._
              _Cynosurus cristatus._

  It is doubtful whether these should not be regarded as awned: if so
  they come near _Nardus_--see p. 130.

_Festuca ovina_, L. (Fig. 59).

Palea rounded on the back, narrow, terete-lanceolate and five-nerved,
tip scaberulous and drawn out to a stiff scabrid point half as long as
the palea, or less. About 3-4 mm. long without the tip-point, 4-5·5 mm.
with it. Rachilla obliquely truncate and concave at its apex.

[Illustration: Fig. 59. _Festuca ovina. a_, spikelet, × about 3-1/2.
_b_, “seed,” nat. size and × about 7. _c_, caryopsis, nat. size and ×
7.]

Caryopsis oblong, somewhat flattened, dark-brown.

  The numerous varieties of _F. ovina_ cannot be distinguished by the
  “seed”: the allied varieties _F. rubra_, _F. duriuscula_, and _F.
  heterophylla_, &c. are sometimes more distinctly awned (see p. 172).
  But difficulties will be found with the whole group, which needs
  revision. This group comprises the grasses so valued on downs and dry
  hill-pastures for sheep-feeding.

  _Festuca sylvatica_, Vill., not a common plant, is also with
  difficulty separable (Fig. 51).

_Cynosurus cristatus_, L. (Fig. 60).

Palea canary yellow to light-brown, lanceolate with rounded back and
the mid-rib prominent as a slight keel and margins infolded, about
4 mm. long (varies from 3-4·5 × 0·5 to 1 mm. broad), scabrid above,
dotted below and acute to acuminate with a scabrid awn-point, often
curved. Caryopsis 2-2·3 mm., somewhat flattened. Rachilla short and
smooth, dilated above.

[Illustration: Fig. 60. _Cynosurus cristatus. a_, “seed” and
caryopsis, nat. size; _b_ and _c_, “seed” × about 8. Note the scabrid
and slightly curved awn-point. Nobbe. Cf. Fig. 64.]

  A valuable and easily recognised grass. _Molinia_, _Holcus_ and
  similar impurities are easily detected: some Fescues are much more
  like it; e.g. _F. tenuifolia_ (see p. 46) in which the apex tapers
  suddenly to a point. _Dactylis_ should also be compared.

            †† Paleæ compressed or distinctly keeled.

               _Molinia cærulea._
               _Kœleria cristata._

  Unimportant, except as impurities among other grass “seeds.”
  _Molinia_ is said to occur as such in samples of _Cynosurus_,
  _Dactylis, Poa trivialis_, Fescues, &c., but it should give little
  difficulty except in comparison with _Glyceria_ (see p. 146).

_Molinia cærulea_ (Mœnch.) (Fig. 61).

“Seed” 3-4 mm. or more, leather coloured or with a bluish tinge. Paleæ
divaricating, the lower keeled and compressed, and tapering to a sharp
point. Rachilla long, oblique and prominent. Smooth tapering, palea
5·5, fruit 2 mm. long.

_Kœleria cristata_, Pers. (Fig. 62).

Palea 6 mm., keeled, entire, no awn but stiffly tapering, ribbed, no
hairs. Rachilla large. Fruit 4·5 mm.

[Illustration: Fig. 61. _Molinia cærulea. a_, “seed,” nat. size; _b_
and _c_, ditto, × about 8; _d_, the caryopsis, nat. size; _e_, ditto, ×
about 7. Note the compressed, keeled and glabrous palea, and the long
slender bone-shaped rachilla. Nobbe.]

[Illustration: Fig. 62. _Kœleria cristata. a_, the “seed” (to the
left) and caryopsis (to the right), nat. size; _b_, “seed,” × about
7. The palea is compressed and keeled, and, like the large rachilla,
glabrous. Nobbe.]

          ** Palea not taper pointed, but mucronate, or two-toothed,
             with a sub-terminal point or spine.

             _Elymus arenarius._
             _Agropyrum repens._
             _Dactylis glomerata._
             _Sesleria cærulea._

_Elymus arenarius_, L. (Fig. 63).

Fruiting palea lanceolate, 13-15 × 3 mm., tough and stiffly hairy or
velvety: 5-7 ribs. Rachilla stout, hairy. Fruit hairy above, 5-11 mm. ×
2·5 × 1·2, somewhat grooved. No keel. Apex of inner palea bifid, outer
mucronate. Fruit shelled.

  Easily distinguished from _Digraphis arundinacea_, which has a basal
  hair-tuft and very different caryopsis; less easily from _Agropyrum_
  and _Lolium_, except in the velvety surface.

[Illustration: Fig. 63. _Elymus arenarius. a_, “seed,” nat. size; _b_
and _c_, the same, × 3. Note the stiff, velvety, bifid and mucronate
outer palea, and the large hairy rachilla. Nobbe.]

[Illustration: Fig. 64. _Dactylis glomerata. a_, spikelet with glumes
removed, nat. size; _b_, ditto, × about 6; _c_ and _d_, “seed,” nat.
size (below) and × about 6. The stiff and slightly curved awn-point is
sub-terminal and arises from between two teeth. Rachilla dilated above.
Nobbe. Cf. Fig. 60.]

_Agropyrum repens_ may have a mucronate awn-point or not. The small
palea 10-12, the caryopsis 5-6 mm. (see p. 169 for description).

  This troublesome weed (Couch-grass) presents similar difficulties
  with _Lolium perenne_ that _Agropyrum caninum_ does with _Lolium
  temulentum_--see p. 168. It is moreover extremely variable.

_Dactylis glomerata_, L. (Fig. 64).

Stiff awn-point just below the two teeth of apex of pale. Rachilla
dilated above. Paleæ 5-6 mm. long exclusive of point, compressed
and inflated, ribbed and ciliate-bristly on keel, the tip incurved.
Caryopsis yellow-brown, ellipsoid, 2 mm.

  An important grass, said to be adulterated with _Lolium_, Fescues,
  _Holcus_, _Molinia_, _Bromus_, &c., most of which should be readily
  detected. The curved tip is an important distinctive character.
  _Cynosurus_ and _Festuca arundinacea_, _F. ovina_ and _F. rubra_
  present resemblances. The seed is larger than that of _Poa_.

  _F. ovina_ and _F. rubra_ are smaller, rounded dorsally, and have no
  keel or cilia: the nerves are less prominent and the rachilla smaller.

_Sesleria cærulea_, Ard.

Palea distinctly toothed at the apex, making it almost three-lobed
and very characteristic; with awn-point; five ribs, serrulate. Fruit
grey-yellow, obovate.

  It is a mountain-and moor-grass of little value.

    +B. “Seed” awned--i.e. the investing palea bears, or tapers into,
        a distinct bristle or hair at least as long as itself or nearly
        so.+

      (_a_) Awn not terminal.

        (1) _Awn stout, either obviously twisted and bent or “kneed.”_

          (i) “Seed” consisting of the glumes as well as paleæ investing
              the caryopsis[13].

            ⊙ _Awn bent but not twisted; glumes free below, ribbed, and
              with stiff short hairs on the keel._

              ≡ _Awn sub-terminal, shorter than the palea, hooked._

                _Holcus lanatus._

  “Yorkshire Fog,” of little use or importance, except that it is
  frequently found as an impurity of other hairy grasses--e.g.
  _Alopecurus_.

  It cannot easily be confounded with any other grass: _Anthoxanthum_
  and _Alopecurus_, _Arrhenatherum_, &c. present superficial
  resemblances only.

  These glumed hairy “seeds” are uncommon and form an easily recognised
  type.

[Illustration: Fig. 65. _Holcus lanatus_. _a_, “seed”--i.e. complete
spikelet--and ditto devoid of glumes, nat. size; _b_, spikelet, and
_c_ the same devoid of glumes, × 7. The “seed” is here composed of the
keeled glumes enclosing two pairs of paleæ and their flowers (_c_): the
upper of these is barren and has a hooked sub-terminal awn to its outer
palea. The lower awnless one is fertile. Nobbe.]

_Holcus lanatus_, L. (Fig. 65).

The “seed” consists of the complete spikelet, separated below the
compressed and acute, keeled glumes; these have hairs on the keel, and
completely enclose the two flowers and their paleæ. Palea ribless,
white to grey, shining, obtuse, that of the upper (male) flower with a
sub-terminal short hook-like awn. Total length about 4-5 mm. Caryopsis
oblong-ovate, grooved. In its palea about 2-3 mm. long and with a few
hairs at the base.

              ≡≡ _Awn dorsal, kneed, longer than the palea._

_Holcus mollis_, L. (Fig. 66).

Palea 2·5 mm., fruit 3·1 mm. long; glumes with stiff hairs or serrulæ
on keel.

The seeds of _Holcus_ often fall from the glumes, but may bring them
away.

[Illustration: Fig. 66. _Holcus mollis._ Type of “double seed,” which
really consists of the entire spikelet (_a_, nat. size; _c_ and _d_, ×
8) comprised of the two glumes enclosing two pairs of paleæ and their
enclosures (_b_, nat. size; _e_, × about 8). The lower pair of paleæ
are devoid of awns and enclose the caryopsis: the upper pair have
stamens only, and the outer palea has a dorsal kneed awn, not twisted
or hooked. Nobbe.]

  _Holcus_ is of little use. The two-flowered spikelets and peculiar
  awns sufficiently distinguish it among the smaller forms. It is said
  to occur as an adulterant in “seed” of _Alopecurus_.

            ⊙⊙ _Awn bent and twisted, basal or nearly so; glumes very
               hairy._

              Δ _Glumes golden brown: one awn straight, one “kneed.”_

                _Anthoxanthum odoratum._

  The grass which gives the scent to new-mown hay. The “seed” is often
  impure, containing a continental species _A. Puelii_ and other hairy
  forms.

[Illustration: Fig. 67. _Anthoxanthum odoratum. a_, “seed” and
caryopsis, nat. size; _b_, the “seed,” and _c_, caryopsis, × about
7. The “seed” consists of the inner hairy glumes, each with a dorsal
awn--one kneed--enclosing the paleæ and caryopsis. The outer pair of
unawned glumes has been removed. Nobbe.]

_Anthoxanthum odoratum_, L. (Fig. 67).

The one-flowered spikelet has four hairy glumes, the outer pair of
which are unequal and awnless: the “seed” consists of the inner pair
of golden-brown hairy and dorsally awned glumes, covering the thin,
membranous, shining, smooth, blunt paleæ and the caryopsis, to which
the inner palea adheres. Total length, without awns, about 3-4 mm.
Palea 1·6 mm. Caryopsis 1·5 mm., brown, shiny, and easily separating.
One awn is short, stiff and straight and inserted above the middle
of its glume; the other longer and sharply bent, inserted about the
middle.

  _Hierochloe_, a rare northern grass, also comes here.

              ΔΔ _Glumes connate below, hairy on the keels._

                 _Alopecurus pratensis._
                 _A. geniculatus._
                 _A. agrestis._

  _Alopecurus_ is very characteristic, and should be carefully examined
  as a type. _A. pratensis_ is a valuable grass and said to be often
  adulterated with the undesirable _A. agrestis_, _Holcus_, &c.
  _Arrhenatherum_ and _Avena_ are easily distinguished by the basal
  hairs, rachilla, &c.

[Illustration: Fig. 68. _Alopecurus pratensis. a_, “seed,” nat. size,
and _b_, _c_, ditto, × 8; _d_, caryopsis, × 7. The “seed” here consists
of the two glumes, connate below and hairy on the keel and ribs,
including the caryopsis enveloped in a single palea with a dorsal awn.
Note remains of stigma in _d_. Nobbe.]

_Alopecurus pratensis_, L. (Fig. 68).

Inner palea absent. Outer palea 5 mm., caryopsis 3 mm. long, often with
remains of the stigma.

The greyish-brown spikelet of _Alopecurus_ easily falls as a whole,
included in the glumes; the palea is loose and delicate.

Glumes connate below, silky-hairy on keel and ribs all the way up. The
palea has a bent dorsal awn, about 5 mm. long.

_Alopecurus geniculatus_, L.

Palea 2 mm., fruit 1·3 mm. long.

The glumes hairy on ribs and keel as in _A. pratensis_: glumes more
obtuse.

_Alopecurus agrestis_, L.

Palea 6 mm., fruit 3 mm. long.

Glumes only ciliate, on ribs and keel, except at the base where the
hairs are longer.

Keel slightly winged.

  Best distinguished from _A. pratensis_ by the glumes, which are
  smoother, broader above the middle, harder and with a few basal hairs.

  The species _A. fulvus_, _A. bulbosus_, and _A. alpinus_ are rare.

          (ii) “Seed” consisting of the paleæ investing the caryopsis,
               freed from the glumes.

            * _Palea at least 14 or 15 mm. long: caryopsis 5-7 mm. [Oat
              type.]_

              _Avena fatua._ _A. pratensis._

              _Avena fatua_, L.

Palea parchment-like, lanceolate-terete, acuminate and bifid at the
apex, rounded on the back and with yellow hairs on the lower part. 15
× 3 mm. Awn brown, twisted and bent, arising from the middle, about
30 mm. long. Caryopsis 7 mm. long, hairy at the top and distinctly
grooved. Rachilla with fine bristles.

_Avena pratensis_, L.

Palea very similar to _A. fatua_, apex 2--4-toothed or bifid, rachilla
with stiffer hairs. Caryopsis about 5 mm. long.

_Avena pubescens_, Huds. is a variety of _A. pratensis_ found on dry
calcareous soils. The caryopsis is very narrow, and the rachilla long
and feathered with hairs. “Seed” shorter than _A. pratensis_, 10-13
mm., and darker in colour.

  _A. fatua_ is an excellent type of the grasses with dorsal twisted
  and bent awns, and easily examined on account of its size. The
  student will find difficulties with other species of _Avena_ and
  _Arrhenatherum_.

  Harz says the stiff hairs of _Avena_ bring about the formation of
  intestinal concretions (phytobezoars) and are therefore dangerous to
  domestic animals.

            ** _Palea not more than 7-10 mm. long._

              † _Caryopsis 4-5 mm. long._

_Arrhenatherum avenaceum_, Beauv. (Fig. 47).

Paleæ papery, ribbed. Awn 13-15 mm., twisted below; paleæ, with a tuft
of hairs below and a ciliate keel, investing the fruit: the whole being
cylindrical, 8-10 mm. × 1·5.

Caryopsis 4-5 mm. × 1·2, fusiform, pubescent. Rachilla hairy.

  The distinctive difference between _Avena_ and _Arrhenatherum_ is in
  the spikelets as a whole. The latter has the lower flower of each
  spikelet male only. Samples contain the “double seeds,” and the awn
  of the upper fertile portion is short (see Fig. 69).

              †† _Caryopsis not more than 3 mm. long. A tuft of hairs on
                 rachilla and base._

                 _Avena flavescens._

  _Aira flexuosa_, distinguished by its nearly basal awn, harder
  texture and darker colour of paleæ, and _Dactylis_--awnless and with
  curved long drawn-out apex--are found as impurities in foreign “seed.”

[Illustration: Fig. 69. _Avena flavescens. c_, “seed,” nat. size;
_a_ and _b_, ditto, × about 7. The dorsal twisted and kneed awn is
very characteristic. Note also the hairy rachilla. The palea is bifid
above--not visible in the lateral view. Nobbe.]

_Avena flavescens_, L. (Fig. 69).

Yellow. Palea about 5 mm. long, five-ribbed, bifid at the apex into
two long slender teeth, closely investing the brownish caryopsis, and
with a sub-dorsal awn 10 mm. long with little or no twist, and hairy at
the base. Rachilla flattened and with white hairs. Caryopsis not much
grooved, fusiform, 2-3 mm. long, glumes unequal, somewhat keeled and
rough.

        (2) _Awn dorsal or basal, fine and hair-like, and little or not
            at all twisted or kneed. “Seed” small._

          * A pencil of silky hairs on base or rachilla. Palea bifid at
            the tip.

            † _Basal hairs longer than palea, and obscuring the awn._

              _Calamagrostis Epigeios._

  Of little importance. _Digraphis_ has no awn.

_Calamagrostis Epigeios_, Roth.

Palea about 3 mm. long with toothed apex and very thin caryopsis 1 mm.
A conspicuous tuft of fine silky hairs, longer than the palea at the
base and on the rachilla.

Awn slender, dorsal, about as long as the palea.

  _C. stricta_, Nutt. and _C. strigosa_, Hartm. are rare.

            †† _Basal hairs shorter than palea._

              ⊙ _Awn brown, bearded in the middle, thickened and white
                above._

                _Aira canescens._

  The student will find considerable difficulties in the various
  species of _Aira_ and _Agrostis_, owing to their small size and
  variability as regards awn and basal hair-tufts. All these are weeds,
  but some occur as adulterants.

_Aira canescens_, L.

“Seed” (apart from the awn, it is very like _Agrostis_) 1·5-2 mm., with
a very thin, smooth, keeled, two-nerved palea, bifid at its apex,
through which the yellow caryopsis shines.

Awn slender, basal, dark-brown, with oblique colourless hairs above the
middle and with a slight swelling above.

The palea has a few hairs on its mid-rib below.

Caryopsis about 1 mm. long.

  This grass is somewhat rare in England. The jointed basal awn,
  with a minute hair-tuft above the middle, is unique, and readily
  distinguishes it when mixed with _Agrostis_.

              ⊙⊙ _Awn not bearded or thickened._

                ≡ _Palea bifid at apex._

                  _Aira caryophyllea._
                  _A. præcox._

_Aira caryophyllea_, L.

“Seed” 1·4-1·6 mm., comma-shaped and dark-brown.

Palea acute, nerveless, inrolled at edges and with a dorsal, kneed,
very fine, dark twisted awn twice as long as the palea: the latter with
two-toothed apex and a basal hair-tuft.

A common impurity in commercial seed.

  _Aira præcox_, L. is very similar, and cannot be distinguished with
  certainty by the “seed,” but has a shorter awn and no basal hairs.
  Apex of palea two-toothed.

                ≡≡ _Palea jagged or toothed, but not bifid._

                   _Aira flexuosa._
                   _A. cæspitosa._

_Aira flexuosa_, L. (Fig. 70).

Palea 5 mm. long, four-toothed at the apex, and caryopsis 2·6 mm. The
fine basal awn waved or kneed, about twice as long as the palea. Fruit
with a groove.

Rachilla hairy. Whole “seed” browner than _Avena flavescens_ (see p.
158).

[Illustration: Fig. 70. _Aira flexuosa. a_, “seed,” nat. size; _c_
and _d_, the same, × about 7; _b_, portion of fruiting panicle, showing
the flexuous rachis; _e_, the caryopsis, nat. size; _f_, ditto, × about
7. Note the basal hairs and twisted awn. Nobbe. Cf. Fig. 44.]

  An almost worthless grass, on sandy soils, but important as an
  impurity in _Avena flavescens_ (see note, p. 158).

_Aira cæspitosa_, L. (Fig. 44).

The palea, about 2·5 mm. long, toothed above, has a fine straight
hair-like basal awn not longer than itself. Caryopsis 1·3 mm., grooved.
Rachilla distinctly hairy.

  Easily distinguished when mixed with _Poa nemoralis_, &c.--e.g. by
  the awn, hairs on rachilla, &c. It requires scrutiny in regard to
  _Agrostis_, which also has no awn or basal hairs.

          ** No basal tuft, or merely a few short microscopic hairs
             below. Paleæ not bifid above.

             _Agrostis canina._
             _A. Spica-venti._
             _A. setacea._

_Agrostis canina_, L., is somewhat larger than _A. alba_. Palea (only
one present, sometimes minute) punctate, 2 mm., with a fine dorsal awn
a little longer than the palea. Caryopsis 1·2 mm. Rachilla obsolete.

  The awn is usually absent from _A. alba_ and its varieties; and when
  present is so small as to be almost negligible.

  _A. canina_ is easily distinguished from _Poa_ by the rachilla in the
  latter, and absence of awn. _Aira_ has basal hairs, &c.

_Agrostis setacea_, Curt., has the awn basal and just projecting beyond
the pointed glumes, and the palea very minute, with a few silky hairs
below.


_Agrostis Spica-venti_, L. (Fig. 49).

Palea 2·4 mm. long, with infolded edges and punctate; a minute rachilla
at its base, and a slender awn, 8-9 mm. or more long, inserted below
the bifid tip. Caryopsis 1·5 mm. A few silky hairs at the base of the
palea.

      (_b_) Awn terminal or slightly sub-terminal, and straight, or at
            least not twisted or “kneed.”

        (1) _Paleæ so closely adherent to the fruit that the terminal awn
            appears to come from the latter [Barley type]. The three
            florets generally coherent._

          ✲ _Awn at least twice the length of the grain._

             _Hordeum sylvaticum._
             _H. murinum._

_Hordeum sylvaticum_, Huds.

Palea scabrid, ribbed above, awn at least twice as long as the very
narrow grain.

_Hordeum murinum_, L.

Lower palea 9-10 mm. long, five-ribbed, lanceolate and wrapped round
and adhering to the fruit (grain), upper palea also ribbed. The grain
about 7-8 mm. × 2 × 1·2, hardly grooved. Awn about 30 mm. long,
serrulate. Rachilla slightly serrulate.

          ** _Awn not twice the length of the grain._

             _Hordeum pratense._
             _H. maritimum._

_Hordeum pratense_, Huds.

Spikelet with a reddish tinge; awn almost smooth, less than 20 mm.
long: not twice the length of the smooth and obscurely nerved grain.

_Hordeum maritimum_, With., similar to _H. pratense_, but softer and
the awn somewhat longer.

  The principal features of the _Hordeum_-grain are the closely
  adherent paleæ and angular fruit, the stiff awn appearing to come off
  from it as in _Barley_. The rachilla remains.

  They are all weeds of no use in agriculture, though _H. pratense_ is
  not uncommon in good pastures.

        (2) _Palea investing the caryopsis, often closely, but not fused
            with it, and its tip and awn quite free._

          * Awn not strictly terminal but sub-terminal, or arising from
            between two teeth or in a sinus at the apex of the palea.

            † Caryopsis thin, flattened and usually 6-10 mm. long, and
              the paleæ hairy.

              ≡ _Palea inrolled, terete-lanceolate-acuminate, or
                linear-lanceolate (barge-shaped). Apical teeth minute
                and pointed._

                Δ _Palea scaberulous or hairy, awn from half to about
                  its own length._

                  _Bromus erectus._
                  _B. asper._

_Bromus erectus_, Huds.

[Illustration: Fig. 71. _Bromus asper_, a barge-shaped “seed” with
terminal awn, nat. size and × about 5. Cf. Fig. 50. Stebler.]

[Illustration: Fig. 72. _Brachypodium sylvaticum_, a barge-shaped
“seed” with terminal awn, natural size and × about 5. Cf. Fig. 77.
Stebler.]

Palea with 5-7 scaberulous ribs, but not hairy, flat above, incurved
below, so that the inner palea is clearly visible. About 10-14 mm.
long and narrowing somewhat suddenly into the smooth stiff awn, shorter
than itself. Indications of a tooth at each side of the base of the
awn. Caryopsis somewhat flattened, thin and long, barge-shaped, 8-10
× 1·5-2 mm., pointed at both ends, brown, hairy at the tip with the
remains of the stigma. “Seed” often purplish. Rachilla long and slender.

  Must be carefully distinguished from _Brachypodium_, which has the
  palea less inrolled and a stouter rachilla.

  _Bromus giganteus_ has a shorter and flatter “seed” and longer awn.

_Bromus asper_, Murr. (Fig. 71).

Palea often reddish, 5-7 ribbed and usually roughly hairy, mid-rib
scaberulous, about 15 mm. long, linear-lanceolate (barge-shaped),
the tip more distinctly two-toothed and tapering more gradually into
the smooth awn, about its own length. Rachilla distinct. Otherwise
resembling _B. erectus_.

  _B. giganteus_ has a shorter “seed” and longer awn.

                ΔΔ _Palea scarcely hairy: awn up to twice its length._

                   _Bromus sterilis._
                   _B. giganteus._

_Bromus sterilis_, L. (Fig. 50).

Palea nearly smooth, somewhat inrolled, terete-lanceolate-acuminate,
tough, red-brown, 12-15 mm. long, seven-ribbed, with a long serrulate
awn (20-30 mm. or more) practically terminal. Ribs serrate. Caryopsis
9-10 mm. long, flattened, thin. Rachilla distinct, smooth, much wrapped
in, widens upwards and is somewhat flattened.

  The very slender and long “seed” and caryopsis distinguish this from
  all but _B. erectus_, which has a shorter awn. Perhaps the awn is
  truly terminal: if so it should go with _Festuca Myurus_, &c. (see p.
  171). The length varies greatly.

_Bromus giganteus_, L.

Palea 7 mm. long and inrolled, the base and rachilla bristly,
indistinctly 5-7 nerved, the tip bifid: sub-terminal awn serrulate,
12-15 mm. long.

Caryopsis 4·5 mm. long, flattened, thin, glabrous.

  The caryopsis is shorter and more ovoid than in other Bromes.

              ≡≡ _Palea expanded above (coracle-shaped), awn from
                 sinus between two blunt or triangular teeth._

                 _Bromus arvensis._

_Bromus arvensis_, var. _mollis_, L. (Fig. 73).

Palea oblong or obovate, somewhat flattened above (coracle-shaped),
distinctly 5-7 ribbed, 8-9 mm. long, not hairy, though the ribs may be
ciliate. Awn smooth, arising from the depression between two teeth or
rounded projections. Caryopsis flattened and thin, 6 × 1·5 mm.; apt to
fall loose from the paleæ.

  In the variety _B. secalinus_ the awn is usually shorter than the
  elliptical palea, and originates in the sinus of a notch (Fig. 74):
  in _B. mollis_ from between two teeth, and is as long as the obovate
  palea.

  _Bromus maximus_ and _B. madritensis_ are both rare.

  The broader nerved paleæ of _B. mollis_ and shorter, fatter
  caryopsis, as well as the longer awn distinguish it from _B.
  secalinus_ and _B. arvensis_. In the other Bromes the palea is more
  inrolled and the “seed” more slender as a rule. The rachilla is
  usually bent above into a slight kink.

  The Bromes are an extremely difficult group. The awn is inserted
  between the two teeth of the palea or just below. The palea smooth or
  ciliate on the nerves or roughly hairy. The fruit is flattened in
  the antero-posterior plane, and usually shines through the closely
  investing palea. A rachilla is visible. In _Brachypodium_ the
  caryopsis is less flattened, and the apex tapers into the awn without
  teeth. In _Lolium_ and _Agropyrum_ the caryopsis is still more
  wheat-like and grooved.

[Illustration: Fig. 73. _Bromus arvensis_, var. _mollis_. _a_, “seed,”
nat. size; _b_ and _c_, the same, × 3. _d_, caryopsis, × about 3.
The awn originates between two teeth of the strongly ribbed palea.
Coracle-shaped type. Nobbe.]

[Illustration: Fig. 74. _Bromus arvensis_, var. _secalinus_. _a_,
spikelet, _b_ and _c_, “seed,” nat. size; _d_ and _e_, the same, × 6.
Nobbe. Cf. Fig. 73.]

  All our Bromes are weeds, but some of them are important adulterants,
  requiring careful examination.

  _B. inermis_ is cultivated, and is a valuable grass. Awn short or
  wanting. Paleæ strongly 5-7 ribbed, inner with a marked central rib,
  closely adhering to caryopsis.

  _B. Schraderi_ is also said to be valuable.

            †† Caryopsis not thin and flattened, corn-like, 3·5-5 mm.
               Palea smooth, inflated, boat-like.

               _Lolium temulentum._

  A weed of cultivation, said to be poisonous to cattle, a possible
  explanation of which may be found in a fungus recently discovered as
  a very constant inhabitant of the tissues under the seed coats.

_Lolium temulentum_, L. (Fig. 48).

Palea ovate, 6-7·5 × 2·5 mm., papyraceous, inflated, smooth, the tip
dry and emarginate with a slender sub-terminal awn its own length or
longer. It tends to adhere to the fruit. Fruit 3·5-5 mm. × 2·5 × 1·5,
somewhat depressed. Rachilla large, cylindrical and smooth.

  _L. perenne_ has no awn, or the merest trace of one. “Seed” 10-12
  mm. long. Boat-shaped. Palea yellow, three-nerved, margins papery.
  Rachilla flat, see p. 143.

          ** Awn terminal, and with no evident teeth at its base.

            ≡ Palea not much inrolled, ovate-lanceolate to
              linear-lanceolate, and therefore boat-or barge-shaped.

              Δ _Very hairy._

_Brachypodium sylvaticum_, Beauv. (Fig. 72).

Palea ribbed and hirsute much like that of _Bromus asper_, but
straw-coloured, shorter (10-12 mm.), linear-lanceolate, more
boat-shaped, and tapering without teeth into the longer (10-13 mm.)
hairy awn. Caryopsis 7-8 mm., less flattened than in _Bromus_, with a
shallow groove. Rachilla smooth.

  _B. pinnatum_ (p. 171) has a much shorter awn, and is nearly glabrous.

  These grasses are weeds, but are said to occur frequently as
  adulterants.

              ΔΔ _Glabrous or nearly so._

                ++ _Palea five-nerved, pubescent._

                   _Agropyrum caninum._

  _Agropyrum repens_ is also often awned and may be described here (see
  also p. 150).

_Agropyrum repens_, Beauv. (Fig. 76).

[Illustration: Fig. 75. _Agropyrum caninum._ Type of boat-shaped “seed”
with sub-terminal awn. _a_, nat. size; _b_, × about 9, but with awn cut
short. Rachilla thicker above and hairy; palea not toothed. Nobbe. Cf.
Fig. 48.]

[Illustration: Fig. 76. _Agropyrum repens._ Awned variety. The awn is
very short and sub-terminal: the rachilla smooth. _a_, the “seed,”
nat. size; _b_ and _c_, ditto, × about 4-1/2. Boat-shaped “seed” with
rounded back. Nobbe. Cf. Fig. 57.]

Palea tough, 10-12 mm. long, ovate-lanceolate, 3-5 ribbed and smooth;
with a short (2-3 mm.) or long (8 mm.) terminal awn or a mere tooth.
Rounded back. Fruit grey-brown, ciliate above, 5-6 × 1·4 × 0·7-0·9 mm.,
depressed, hardly grooved, adhering to the palea. Rachilla smooth or
not, and narrowed below.

  A noxious weed (see p. 150) and hence should be carefully excluded
  from “seeds.”

_A. caninum_, Beauv., has a longer (10 mm. or more) and rougher awn,
and is smaller (about 8 mm.), but otherwise very similar. Palea smooth
except at the five-nerved apex. Rachilla thickened above, and hairy
(Fig. 75).

  _Elymus_ differs from _Agropyrum_ in its harder velvety palea,
  no awn, and its club-like velvety rachilla. It is also larger
  altogether, as a rule.

[Illustration: Fig. 77. _Brachypodium pinnatum._ Type of boat-shaped
“seed” with awn. _a_, nat. size; _b_ and _c_, × 7. Nobbe. Cf. Fig. 72.]

                ++++ _Palea seven-ribbed, smooth._

                     _Brachypodium pinnatum._

_Brachypodium pinnatum_, L., is similar, but the palea more open and
boat-like and narrows more suddenly above into the smooth awn which
is shorter than itself (Fig. 77). Length 8-9 mm. The caryopsis is,
however, much more slender than in _Agropyrum_.

  For distinction from _B. sylvaticum_, see above. The inner palea is
  ciliate and more delicate than in _Agropyrum_.

            ≡≡ Paleæ rolled round the “seed” which is terete and
               tapering gradually into a stiff awn.

              Δ _Awn longer than the palea._

                _Festuca Myurus._

  See also _Festuca ovina_, _Cynosurus_, &c., p. 147, and _Arundo_.

_Festuca Myurus_, L. (Fig. 80).

“Seed” 5-7 mm. without the long (10 mm.) awn, tapering and slender
(like _Nardus_), grey or brown. Finely mamillate upwards. Rachilla
small.

              ΔΔ _Awn shorter than palea._

                 _Festuca ovina_ (var. _rubra_).
                 _Nardus stricta._

  _Aira flexuosa_, _Molinia_ and other moor-grasses occur with these
  narrow-leafed Fescues, but are easily distinguished: _Molinia_ by
  having no awn and being shorter and stouter, and _Aira flexuosa_ by
  the dorsal awn and basal hairs.

_Festuca rubra_, L. (Fig. 78).

“Seed” pale brown with rosy tinge, 3-5 mm. long without the awn,
smooth, or slightly hairy upwards. Caryopsis 2-3·5 mm., compressed,
with a shallow broad flat furrow on the ventral face and a median long
“hilum.” Rachilla cylindrical, smooth, dilated above.

[Illustration: Fig. 78. _Festuca ovina_, var. _rubra_. _a_, “seed,”
nat. size; _b_ and _c_, ditto, × about 7. Nobbe. Cf. Fig. 59.]

[Illustration: Fig. 79. _Festuca ovina_, var. _heterophylla_. _a_,
spikelet, × about 3-1/2; _b_, “seed,” and _c_, caryopsis, nat. size;
_d_ and _e_, “seed,” and _f_, caryopsis, × 7. Nobbe.]

The variety _F. heterophylla_ has narrower and longer “seeds,” and a
hispid rachilla. Palea 5-6 mm.: caryopsis 3·5-4·5 mm. (Fig. 79).

Perhaps _Bromus sterilis_ should also come here (see p. 165).

  With regard to these Fescues the student may note that _F. ovina_,
  var. _tenuifolia_, has the smallest (4-5 mm.) and most ovoid “seeds,”
  usually golden brown in colour. _F. rubra_ is darker and larger (5-6
  mm.), as is also _F. duriuscula_ (6-7 mm.): the latter is also
  narrower, with toothed palea, tapering suddenly at the base and more
  awned. _F. heterophylla_ is much like _F. duriuscula_, but the palea
  less toothed, and it tapers gradually at the base. The whole group is
  very difficult, and needs attention.

[Illustration: Fig. 80. _Festuca Myurus. a_, “seed,” nat. size; _b_
and _c_, ditto, × about 6. Compare Fig. 50. Nobbe.]

[Illustration: Fig. 81. _Nardus stricta._ Type of cylindrical “seed”
with a terminal stiff awn, here serrulate; _c_, “seed,” nat. size; _a_
and _b_, ditto, × 8. Compare Fig. 50. Nobbe.]

_Nardus stricta_, L. (Fig. 81).

Outer palea tough and fused, 10-12 mm. long, narrow, lanceolate and
tapering gradually into the stiff, serrulate, terminal awn shorter
than itself. Inner palea minutely toothed at the apex and without awn,
loosely enclosing the red-brownish yellow to bluish grey fruit which
has no groove. “Seed” 4-6 mm. × 0·6 × 0·5 (without the awn), more or
less triangular in section and serrulate on angles above.




BIBLIOGRAPHY.


  BENTHAM AND HOOKER, _British Flora_, London, 1896.

  BONNIER and LAYENS, _Nouvelle Flore de France_, Paris, 1887.

  BRUNS, _Der Grasembryo_ in _Flora_, 1892, vol. LXXVI.

  BURCHARD, _Die Unkrautsamen der Klee-und Grasarten_, Berlin, 1900.

  DARWIN, _Power of Movement in Plants_, London, 1880.

  DUVAL JOUVE, in _Mémoires de l’Acad. des Sciences de Montpellier_,
    1871, vol. VII.

  FREAM, _Elements of Agriculture_, London, 1892.

  GROB, in _Bibliotheca Botanica_, H. 36, 1896.

  GUÉRIN, _Recherches sur le développement du Tégument &c. des
    Graminées_ in _Ann. d. Sc. Nat._ 1899.

  GÜNTZ, _Unters. ü. d. anatomische Structur d. Grasblätter_, Leipzig,
    1886.

  HACKEL, in Engler’s _Natürliche Pflanzenfamilien_, II. Th. 2 Abth.
  1887.

  HARZ, _Landwirthschaftliche Samenkunde_, Berlin, 1885.

  HOLZNER, _Beitr. zur Kenntn. d. Gerste_, Munich, 1888.

  _Index Kewensis_, London, 1893-95.

  JACKSON, _A Glossary of Botanic Terms_, London, 1900.

  KIENITZ-GERLOFF, _Botanik für Landwirte_, Berlin, 1886.

  NOBBE, _Handbuch der Samenkunde_, Berlin, 1876.

  PARNELL, _British Grasses_, London, 1845.

  PÉE-LABY, in _Annales des Sc. Naturelles_, 1898, vol. VIII.

  PERCIVAL, _Agricultural Botany_, London, 1900.

  PFITZER, in Pringsh. _Jahrb. f. wiss. Bot._ B. VII.

  SCHMID, in _Bot. Centralbl._ 1898, B. LXXVI.

  SCHWARZ, _Forstliche Botanik_, Berlin, 1892.

  SCHWENDENER, in _Sitzungsber. d. Akad. Berlin_, 1889 and 1890.

  SETTEGAST, _Die landwirthschaftl. Sämereien u. d. Samenbau_, Leipzig,
    1892.

  SINCLAIR, _Hortus gramineus Woburnensis_, London, 1824.

  SOWERBY, _The Grasses of Great Britain_, London, 1861.

  STEBLER and SCHROETER, _The Best Forage Plants_, London, 1889.

  SUTTON, _Permanent and Temporary Pastures_, London, 1886.

  TRIMEN, Article _Grasses_, in _Encyclopædia Britannica_, 9th ed.

  VAN TIEGHEM, _Morphol. de l’embryon &c. chez les Graminées_ in _Ann.
    des Sc. Nat._ 1897.

  VESQUE, _Traité de Botanique Agricole &c._ 1885.

  WARMING, _Lehrb. d. Oekologischen Pflanzengeogr._ Berlin, 1896.

  WITTMACK, _Gras- und Kleesamen_, Berlin, 1873.




FOOTNOTES:

[Footnote 1: Some foreign grasses (_Andropogon_, _Panicum_, &c.) have
solid stems, and in _Psamma_ and some others the lower parts may be
solid.]

[Footnote 2: Leaf-stalks occur in tropical Bamboos.]

[Footnote 3: Tropical Bamboos branch in the upper parts and are woody.
_Dinochloa_ and _Olyra_ are climbing grasses.]

[Footnote 4: Except, of course, in cases of virgin ground rapidly
occupied by the seedlings.]

[Footnote 5: The most marked exceptions are the lemon-scented grasses
(especially _Andropogon_) of India and Ceylon.]

[Footnote 6: The pale flanking lines seen in many grasses on each side
of the mid-rib are the series of motor-cells referred to on p. 25.]

[Footnote 7: They may have short microscopic asperities, but there are
no distinct long hairs.]

[Footnote 8: Very like a Poa when opened out, but the leaves are
scabrid at the sheaths.]

[Footnote 9: Strictly speaking a spike is an axis bearing sessile
_flowers_--not sessile _spikelets_: in Grasses, however, the
conventional abbreviated term is sanctioned by long usage. The same
applies to the panicle, &c.]

[Footnote 10: See note, p. 87.]

[Footnote 11: See note, p. 87.]

[Footnote 12: This term does not necessarily imply any botanical
relationship with the true Millets (_Panicum_), but merely that the
caryopsis is short and broad as in these grasses.]

[Footnote 13: In cases where the “seed” has fallen from the glumes the
sample will usually show some of the latter lying loose.]




INDEX,

GLOSSARY AND LIST OF SYNONYMS.


Figures in bold type (+25+) refer to pages whereon the species or
subject is more particularly dealt with; figures in italics (_25_)
refer to pages containing illustrations.

  Achene, 123

  Acicular--bristle-like

  Acuminate--tapering to a long point, 21, 139, 146, 147

  Acute--simply pointed, 19, 21

  Adaptations, 20, 24, 36, 37, 70, 124, 125, 132

  Adventitious roots, 8, 131

  Agriculture, 2, 3

  _Agropyrum_--Wheat-grass, 11, 14, 22, 25, 26, 36, 49, 50, 51, 57, 69,
  88, 90, 91, +106+, 107, 108, 144, 150, 167, 170, 171;
    _A. caninum_, 7, 21, 28, 34, +57+, +80+, 92, +107+, 150, 168, _169_,
      +170+;
    _A. junceum_--var. of _A. repens_, 21, 29, 33, 35, 36, 57, _66_,
      +81+, 102, 107;
    _A. repens_, 7, 30, +57+, +80+, 81, 93, 102, +106+, 149, +150+,
      _169_, +170+

  _Agrostis_--Bent-grass, 7, 15, 22, 25, 49, 50, 51, 52, 53, 57, 82,
  88, 89, 91, 103, +104+, 105, 112, 118, 125, 136, 137, 141, 144, 145,
  159, 160, +161+;
    _A. alba_, 7, 11, 13, 14, 28, 29, 32, 33, 34, 51, 52, 69, 92, +104+,
      144, +145+, 162;
    _A. canina_, 7, 11, 20, 28, 29, 37, 51, 52, +104+, 161, +162+;
    _A. setacea_, 31, 104, 161, +162+;
    _A. Spica-venti_, 31, 104, _130_, 161, +162+;
    _A. stolonifera_--var. of _A. alba_, 14, +51+, 52, 104, +145+;
    _A. vulgaris_--var. of _A. alba_, 29, 51, 52, 66, 104, +145+

  _Aira_--Hair-grass, 6, 20, 21, 36, 48, 88, 89, 90, 91, 103, 104, 105,
    106, 110, 112, +117+, 118, 125, 127, 138, 141, 144, 145, 159, 162;
    _A. alpina_--var. of _A. cæspitosa_;
    _A. canescens_, 8, 11, 14, 32, +47+, 66, 78, 91, 112, +159+;
    _A. caryophyllea_, 8, 10, 14, 29, 32, +46+, +118+, +160+;
    _A. cæspitosa_, 6, 11, 14, 22, 23, 25, 28, 33, 37, 41, +47+, 48, 63,
      _65_, 68, 69, +77+, 104, 106, +117+, _128_, 160, +161+;
    _A. flexuosa_, 7, 11, 14, 29, 33, 34, +46+, 68, 70, _71_, +79+,
      +118+, 158, +160+, _161_, 171;
    _A. montana_--var. of _A. flexuosa_;
    _A. setacea_--var. of _A. flexuosa_;
    _A. præcox_, 8, 10, 29, 30, 32, +47+, 91, +112+, 160

  Air-spaces, 21, 39, 40, 62

  Aleurone layer, _121_, _122_, 123

  _Alopecurus_, 25, 53, 55, 88, 89, 90, 93, +101+, 109, 110, 119, 124,
    152, 153, 155;
    _A. alpinus_, 31, 101, 156;
    _A. agrestis_, 7, 18, 30, 50, 52, 53, +101+, 155, +156+;
    _A. bulbosus_--var. of _A. geniculatus_, 8, _9_, 156;
    _A. fulvus_--var. of _A. geniculatus_, 156;
    _A. geniculatus_, 7, _9_, 11, 14, 15, 28, 29, 33, 40, 48, 52, 53,
      +101+, 155, +156+;
    _A. pratensis_, 7, 11, 13, 14, _18_, 28, 32, 49, 50, 51, +52+, 55,
      +82+, +101+, _155_, +156+

  Alpine Foxtail--_Alopecurus alpinus_

  Alpine Meadow-grass--_Poa alpina_

  Alpine Poa--_Poa alpina_

  Alps, 36, 37

  _Ammophila--Psamma_;
    _A. arundinacea_--_Psamma arenaria_

  _Amphicarpum_, 120

  Anatomy, 62-71, 95

  _Andropogon_, 4, 27

  Andropogoneæ, 122

  Animal-distribution of seeds, 125

  Animals killed by grasses, 127

  Annual Beard-grass--_Polypogon monspeliensis_

  Annual grasses, 10, 11, 37, 43, 59, 114

  Annual Meadow-grass--_Poa annua_

  Anther, _93_, 94, 119

  Anthesis--the period of opening of the flower, 96

  _Anthoxanthum_--Vernal grass, 11, 13, 22, 26, 27, 36, 56, 58, 60, 83,
    _87_, 88, 90, 91, 94, 97, 110, 119, 124, 136, 152, _154_;
    _A. odoratum_, 7, 28, 32, 33, 34, +57+, +76+, +102+, +103+, +154+;
    _A. Puelii_, 67, 154

  Anti-ligular peg, 41

  _Apera--Agrostis_;
    _A. Spica-venti_--_Agrostis Spica-venti_

  Apex of leaf, 19, +21+, +22+

  Apogamy, 134

  Appressed hairs, 65

  Aquatic grasses, 27, +28+, 39, 62, 103, 111, 112, 113

  Arctic species, 37

  _Aristida_, 36;
    _A. hygrometrica_, 127

  _Arrhenatherum_--False Oat, 6, 11, 13, 14, 17, 26, 32, 55, 56, 58,
    60, 61, 66, 89, 90, 91, 92, 119, 152, 155, 157;
    _A. avenaceum_, 6, 8, 25, 28, 33, 34, +56+, 66, +77+, _93_, +106+,
      _129_, +157+

  _Arundo_--Reed, 11, 14, 19, 20, 37, 40, 68, 69, 90, 91, 93, 103, 125,
    130, 131, 139, 146, 171;
    _A. Donax_, 21, 75;
    _A. Phragmites_, 2, 6, 29, 32, 40, +51+, 55, 66, +75+, +138+

  Asperities--minute stiff hairs giving roughness to the touch, 24, 45,
    65, 66, 75, 77, 127

  Auricles--ear-like projections at base of leaf-blade, 22, 133

  _Avena_, _5_, 15, 21, 23, 47, 54, 56, 88, 89, 90, 91, 92, 95, 104,
    106, +116+, 117, 125, 127, 138, 155, 157, _158_;
    _A. alpina_--var. of _A. pratensis_;
    _A. elatior_--_Arrhenatherum avenaceum_;
    _A. fatua_, 28, 77, +117+, +156+, 157;
    _A. flavescens_, 7, 11, 13, _18_, 26, 28, 56, +60+, 61, +81+,
      +117+, +158+, 161;
    _A. pratensis_, 7, 11, 14, 20, 21, 22, 25, 27, +47+, 56, 61, 63,
      66, 81, +117+, 156, +157+;
    _A. pubescens_--var. of _A. pratensis_, 16, 26, 27, 32, 33, 56,
      +61+, 68, +157+;
    _A. strigosa_--var. of _A. fatua_

  Aveneæ, 122

  Awn, 91, 92, +95+, 99-118, +125+, _126_, 127, _128_, _129_, +130+,
    _131_, 142, 144, 151, 153, 154, 159, 160, 162, 163, _164_, 166,
    _167_, 168, _169_, _170_, 171, _173_

  Awned grasses, +92+, 99-101, 102, 103, 104, 105, 106, 107, 111, 112,
    113, 114, 115, 116, 117, 151-174

  Awned Nit-grass--_Gastridium lendigerum_

  Awnless Brome--_Bromus inermis_

  Awnless grasses, +93+, 104, 105, 107, 108, 109, 110, 111, 112, 138-151

  Awn-point, 114, 115, 116, _123_, 131, _150_


  Ballast plants, 30

  Bamboos, 1, 5, 6, 37, 38, 96, 97, 123

  _Bambusa_, 96

  Barge-shaped “seeds,” 128, 163, _164_, 168

  Barley--_Hordeum_, 120, 132, +133+, 163

  Barley-type of “seed,” 138, 162

  Barren Brome--_Bromus sterilis_

  Barren flowers, 86, 89, 90, 99, 100

  Basal-awn, 92, _128_, _129_, 130, 159

  Basal hair-tufts, 138, _158_, 159, 160, 161

  Base of leaf, _18_, _19_, 20, 22

  Bast-sclerenchyma, 70

  Bearded Darnel--_Lolium temulentum_

  Bearded Wheat-grass--_Agropyrum caninum_

  Beard-grass--_Polypogon_

  Bent-grass--_Agrostis_

  Bent-grass--_Agrostis canina_

  Bermuda grass--_Cynodon Dactylon_

  Biennial grasses, 10, 43

  Bifid--cleft into two teeth, 95

  Bitter-tasting grasses, 58, 59

  Blade of leaf, 17, _18_, _19_, 20, 22, _23_, _24_, 26

  Blue Moor-grass--_Sesleria cærulea_

  Boat-shaped “seeds,” 127, _128_, _129_, 138, 142, _143_, 144, 167,
    168, _169_, _170_

  Bœhmer’s Phleum--_Phleum Bœhmeri_

  _Brachypodium_--False Brome, 11, 14, 20, 60, 70, 88, 90, +107+, 108,
    109, 165, 167;
    _B. pinnatum_, 7, 34, +61+, +78+, 93, +107+, 130, 168, _170_, +171+;
    _B. sylvaticum_, 7, 26, 28, 33, 34, 60, +61+, 76, 78, 92, +107+,
      128, _164_, +168+, 171

  Bracteoles, 95, 96, 97

  Bracts, 94, 97

  Branching, 6, 11

  Branching of inflorescence, 83

  Bristle-grass--_Setaria_

  Bristle-leafed Bent-grass--_Agrostis setacea_

  Bristle-like leaves, _16_, 21, _24_, 45

  Bristle Oat--_Avena strigosa_

  Bristles, 67, 125, 130

  _Briza_--Quaking-grass, 14, 16, 22, 25, 90, 91, 92, 104, 136;
    _B. media_, 8, 11, 17, 27, 32, +45+, 66, +77+, +112+, +142+;
    _B. minor_, 10, 17, +45+, 112, 142

  Brome--_Bromus_, 166, 167

  _Bromus_--Brome-grass, 6, 10, 14, 17, 26, 44, 51, 59, 61, 76, 90, 91,
    92, 95, 103, 104, 107, +115+, 117, 144, 151, 168;
    _B. Alopecurus_, 95;
    _B. arvensis_, 7, 8, 11, 27, 30, 32, +43+, 44, +76+, 108, +115+,
      128, +166+, _167_;
    _B. asper_, 6, 11, 17, 20, 22, 26, 28, 33, 34, +43+, 44, 59, 76,
      +115+, 116, _164_, +165+, 168;
    _B. commutatus_--_B. racemosus_;
    _B. diandrus_--_B. madritensis_;
    _B. erectus_, 7, 11, 13, 14, +43+, 51, 70, 100, +164+, 165, 166;
    _B. giganteus_, 6, 11, 28, 33, 34, +43+, 44, 51, 76, 82, +115+,
      116, 165, +166+;
    _B. inermis_, 13, 22, 31, +43+, 167;
    _B. madritensis_, 31, 116, 166;
    _B. maximus_, 31, 116, 166;
    _B. mollis_--var. of _B. arvensis_, 8, 26, +43+, 44, 108, 115, 143,
      +166+, _167_;
    _B. multiflorus_--var. of _B. arvensis_;
    _B. racemosus_--var. of _B. arvensis_;
    _B. Schraderi_, 167;
    _B. secalinus_--var. of _B. arvensis_, 115, 166, _167_;
    _B. sterilis_, 7, 11, 27, 30, 32, +43+, 44, +76+, +116+, _131_,
      +165+, 172

  Brown Bent--_Agrostis canina_

  Buds, 12

  Bulbous Meadow-grass--_Poa bulbosa_

  Bulbous Poa--_Poa bulbosa_

  Bulbs, 8, 37, 114


  _Calamagrostis_--Small reed, 29, 40, 88, 89, 125, 138;
    _C. Epigeios_, 31, 70, 78, +103+, +159+;
    _C. lanceolata_, 31, 66, 103, +138+;
    _C. strigosa_, 103, 159;
    _C. stricta_, 31, 103, 159

  Canary grass--_Phalaris canariensis_

  Carpel, 97, 121

  Caryopsis--the true fruit of the grass, _121_, _122_, 123, 124, 127,
    _128_, 132, +134+, 135

  _Catabrosa_--Whorl-grass, 14, 21, 23, 29, 40, 63, 84, 88, 90, 91, 92,
    104, 105, 118, 146;
    _C. aquatica_, _12_, 25, 31, 73, +112+, 142

  Cat’s-tail grass--_Phleum_

  Cat’s-tail type of inflorescence, 100

  Cells, 65

  Cereals, 1

  Chaff, 85, 134

  Chalk-fleeing, 35

  Chalk species, 27, +32+, 35

  _Chamagrostis_--_Mibora_

  Chlorophyll, 2, 62, 70, 72, 73, 95

  _Cinna_, 97

  Circular shoot sections, _16_, 43

  Classification according to anatomical characters of leaf, 72-82

  Classification according to floral characters, 97, 99-118

  Classification according to characters of seed, 135-174

  Classification according to vegetative characters, 39-61

  Classification of seedlings, 133

  Clay species, 32

  Cleistogamous--when pollination and fertilisation are completed in
     flowers which do not open, 120

  Climbing grasses, 6

  Close panicle--an inflorescence in which the primary branches do not
    diverge widely from the rachis, 110

  Cock’s-foot--_Dactylis glomerata_, 83

  Cockspur Panicum--_Panicum Crus-galli_

  Collar, 58, 123

  Coloured nodes, 15

  Coloured sheath, 18

  Coma, 125

  Common Cat’s-tail--_Phleum pratense_

  Common Dog’s-tail--_Cynosurus cristatus_

  Common Foxtail--_Alopecurus pratensis_

  Common Mat-grass--_Nardus stricta_

  Common Quaking-grass--_Briza media_

  Common Reed--_Arundo Phragmites_

  Compact Brome--_Bromus madritensis_

  Composites, 2, 125

  Compressed shoots, 15, _16_, 40, 41, 48, 53

  Conduplicate--folded, 15, _16_, 20, 63

  Convolute--inrolled, 15, _16_, 63

  Copses, grasses of, 28, 34

  Coracle-shaped “seeds,” 128, _137_, 166, _167_

  Cord-grass--_Spartina stricta_

  Coriaceous--leathery, 21

  Corn, 1

  Corn-field species, 28

  Corn-type of fruit, 136, 138, 167

  _Corynephorus canescens_--_Aira canescens_

  Cotton-grass--_Eriophorum_

  Couch-grass--_Agropyrum repens_.
    _See also_ Twitch, 150

  Creeping Fescue--_Festuca rubra_

  Creeping grasses, _12_, 13, 14, _15_

  Creeping grass-seeds, 127

  Creeping Soft-grass--_Holcus lanatus_--_Holcus mollis_

  Creeping stem, 12

  Crested Dog’s-tail--_Cynosurus cristatus_

  Crested Kœleria--_Kœleria cristata_

  Cross-breeds, 120

  Cross-fertilisation, 119, 120

  _Crypsis_, 123

  Culms, 14, 37, 83

  Curved Lepturus--_Lepturus incurvatus_

  Cuspidate--ending suddenly in a short point, 135

  Cut-grass--_Leersia_

  Cuticle, 68, 70

  Cutinized, cuticularized--impregnated with corky substance, 64

  Cylindrical inflorescence, 90

  Cylindrical “seed,” _173_

  _Cynodon_--Dog’s-tooth grass, 14, 65, 67, 69, 87, 90, 105;
    _C. Dactylon_, _15_, 31, +72+, 137

  _Cynosurus_--Dog’s-tail, 14, 18, 25, 49, 50, 52, 81, 88, 89, 90, 93,
    103, 130, _148_, 151, 171;
    _C. cristatus_, 7, 11, 13, _23_, 28, 32, +50+, +80+, +108+, 147,
      +148+;
    _C. echinatus_, 100, 108


  _Dactylis_--Cock’s-foot, 11, 13, 14, 16, 20, 26, 41, 63, 83, 88, 89,
    90, 91, 93, 103, 148, 158;
    _D. glomerata_, 7, _16_, 17, 27, 32, 33, 34, +41+, 65, 66, 69,
      +74+, +109+, 149, _150_, +151+

  Darnel--_Lolium perenne_--_Lolium temulentum_

  Decumbent Heath-grass--_Triodia decumbens_

  Dehiscent fruits, 123

  Depauperated--starved and consequently dwarfed, 109

  _Deschampsia cæspitosa_--_Aira cæspitosa_

  _Deschampsia flexuosa_--_Aira flexuosa_

  _Digitaria_--_Panicum_

  Digitate--spread out like fingers, _15_

  _Digraphis_--Reed-grass, 6, 11, 13, 26, 40, 41, 51, 55, 69, 73, 75,
    90, 91, 92, 103, 131, 139, 146, 159;
    _D. arundinacea_, 6, _16_, _23_, 29, 32, +54+, 64, +75+, +103+,
      +139+, 150

  Dimensions of grasses, 6

  _Dinochloa_, 6

  Diœcious, unisexual, the male and female flowers being on separate
    plants, 119

  Disarticulation of fruits, _124_

  Dissemination, 125, 127

  Distichous--in two ranks on the axis, 106

  Distribution of grasses, 2, 37, 38

  Distribution of seeds, 124-127

  Distribution of sexes, 119

  Ditches, grasses of, 28, 29

  Dog’s-tooth grass--_Cynodon Dactylon_

  Dorsal awn, 92, 112, 116, 130, 159

  Double seed--grass “seed” where the remains of a second flower come
    away with the first, _152_, _153_

  Downs, grasses of, 29

  Downy Oat--_Avena pubescens_

  Dry leaves, 21

  Dry situations, 24, 26, 29

  Dry soils, 29, 32

  Duration, 10

  Dwarfed species, 6


  Early Hair-grass--_Aira præcox_

  Ears, _19_, 22, 57, 59

  _Echinochloa_--_Panicum_

  Effects of grasses on soil, 35, 36

  Egg-cell, 121

  _Eleusine_, 123

  Elliptical shoot-section, 16, 44

  _Elymus_--Lyme-grass, 6, 13, 14, 21, 22, 25, 36, 48, 57, 63, 65, 69,
    79, 90, 92, 102, 170;
    _E. arenarius_, 6, 29, 33, 35, 36, +48+, 66, _67_, +108+, +149+,
      _150_

  Embryo, 121, 131, 133

  Embryo-sac, 121

  Embryonic bud--plumule, 123

  Embryonic roots, 123, 133

  Endosperm, 120, _121_, _122_, 123

  Energy stored in leaves, 2, 3

  Entire--not cut: with unbroken outline, 19

  Entire sheath, 17

  Entire-sheathed grasses, 17, 39, 113, 115

  Epidermis, 25, 36, 62-67, 70, 76, _122_

  Equitant--one folded leaf straddling over another, 39, 41

  _Eriophorum_, 3

  Extra-vaginal shoots, 12


  False Oat--_Arrhenatherum avenaceum_

  Female flowers, 89

  Fertile flowers, 86, 89, 90

  Fertilisation--the fusion of the nucleus of the pollen-tube with that
    of the egg-cell, 121

  Fescue--_Festuca_, 115, 130, 137, 144, 148, 151, 172

  _Festuca_--Fescue, 2, 6, 7, 15, 21, 25, 36, 49, 51, 53, 90, 91, 92,
    108, 109, 110, 113, 114, 116, _124_, 144, _147_;
    _F. arundinacea_--var. of _F. elatior_, 144, 151;
    _F. calamaria_--_F. sylvatica_;
    _F. duriuscula_--var. of _F. ovina_, 46, _69_, +78+, 80, 147, 172,
      173;
    _F. elatior_, 6, 7, 11, 13, 14, 18, 19, 22, 25, 28, 32, 44, +50+,
      51, 63, _64_, 82, _84_, 108, 111, 115, +116+, 128, 131, _143_,
      +144+;
    _F. gigantea_--_Bromus giganteus_;
    _F. heterophylla_--var. of _F. ovina_, 13, 46, 69, 71, 78, 80, 147,
      +172+, 173;
    _F. uniglumis_, 31, 92, 111;
    _F. loliacea_--var. of _F. elatior_, 90, 108;
    _F. Myurus_, 8, 10, 14, 19, 20, 28, +46+, 90, 91, 92, 99, +111+,
      115, 130, 166, +171+, _173_;
    _F. ovina_, 7, 8, 11, 13, 14, _19_, 20, 22, _24_, 28, 32, 33, 36,
      +45+, 46, 68, 69, 70, +79+, +111+, 112, 115, +116+, 134, +147+,
      151, 171, _172_;
    _F. pratensis_--var. of _F. elatior_, 7, _19_, _24_, 49, 63, _64_,
      _84_, 111, _143_, +144+;
    _F. procumbens_--_Poa procumbens_;
    _F. rigida_--_Poa rigida_;
    _F. rubra_, var. of _F. ovina_, 7, 13, 14, 18, _24_, 33, 46, 69,
      78, 80, 147, 151, +171+, _172_;
    _F. sabulicola_--_F. rubra_, 46;
    _F. sciuroides_--var. of _F. Myurus_, 25, 26, 46;
    _F. sylvatica_, 6, 11, 14, 28, 34, +116+, _131_, 147;
    _F. tenuifolia_--var. of _F. ovina_, 46, 148, 172;
    _F. vivipara_--var. of _F. ovina_

  Festuceæ, 122

  _Fibichia umbellata_--_Cynodon Dactylon_

  Fibrous roots, 8

  Fibrous Twitch--_Agropyrum caninum_

  Field Brome--_Bromus arvensis_

  Filament, 94

  Fine Bent--_Agrostis vulgaris_

  Finger-grass--_Panicum glabrum_

  Fiorin--_Agrostis alba_

  Firing, 35, 38

  Flanking lines, 41, 53, _63_, 73, 74

  Flat leaves, 20, 47, 77

  Flat shoots, 15, _16_, 20

  Flattened Meadow-grass--_Poa compressa_

  Flavour, 27

  Fleshy fruits, 123

  Floating leaves, 39

  Floating Foxtail--_Alopecurus geniculatus_

  Floating Meadow-grass--_Glyceria fluitans_

  Floating Sweet-grass--_Glyceria fluitans_

  Floral diagram, _94_, 95, _96_

  Flower, 83, _84_, _85_, +86+, _87_, 89, 90, _93_, _94_, 95, _96_, 97,
    99, 105, 106, 112

  Flowering glume--the outer palea

  Flowering stem, 83, 84

  Flying Bent--_Molinia cærulea_

  Folded leaves, 15, _16_, 20, 24, 25, 63, _69_, 70, 74

  Foreign grasses, 30

  Forestry, 3

  Forest species, 27, 28, 33

  Form of lamina, 19, 20

  Foxtail grass--_Alopecurus_

  Foxtail type of inflorescence, _9_, 88, 100

  Fructification--fruiting, 120

  Fruit, 119, 123, 125, _126_, _129_, +134+, +135+-+174+

  Fruit-coats, 121, 122

  Functions of awns, 95, 125, _126_, 127

  Functions of ears, 19

  Functions of leaves, 2

  Functions of ligule, 18, 19

  Functions of lodicules, 96

  Functions of spear, 132

  Furrows, 23, 78


  _Gastridium_--Nit-grass, 90, 91, 101, 103, 105;
    _G. lendigerum_, 31

  Germination, 123, +131+-+133+

  Germination of pollen-grain, _120_, 121

  Giant Fescue--_Festuca gigantea_

  Girders--supporting bands of sclerenchyma running in the principal
    ribs and ridges, _63_, _64_, 65, _66_, _67_, +68+, _69_, 70, 71,
    74-80

  Glabrous--devoid of hairs, 18, 19, 22, 26, 45, 48, 80, 168

  Glaucous--pale sea-green, usually due to a waxy bloom, 22

  Glume, 85, 86, _87_, +91+, +92+, 93, +94+, 95, 99-118, 124, 125, 127,
    130, 134, 135, 136, 151, _152_, _153_, _154_, _155_, 156

  _Glyceria_--Sweet-grass, 6, 14, 20, 21, 37, 40, 54, 67, 90, 91, 92,
     136, 137, 138, 146, 148;
    _G. aquatica_, 6, 11, 16, 17, 25, 26, 28, +39+ 54, 69, +73+, 103,
      111, 112, +113+, 142, +145+;
    _G. distans_--_Poa distans_;
    _G. fluitans_, 6, 11, 16, 17, 25, 28, 32, +39+, 40, 54, 64, 66, 69,
      +73+, +111+, 113, _128_, +145+;
    _G. maritima_--_Poa maritima_;
    _G. procumbens_--_Poa procumbens_;
    _G. rigida_--_Poa rigida_

  Grain, 86, 95, 121, _122_, 127, 135

  Graminaceæ, characters, 3, 36, 37

  Gramineæ, _see_ Graminaceæ

  Grass, origin of the word, 3

  Grass carpets, 2, 37

  Grasses, identification of, 3, 4

  Grazing, 27

  Grey Hair-grass--_Aira canescens_

  Grooved leaf, _69_, 70, _71_, 79

  Grooved sheath, 18

  _Gynerium_, 89


  Habit, 13, 34

  Habitats, 27-31

  Hair-grass--_Aira_

  Hairs, _18_, 19, 21, 24, 26, 62, 64, 66, 67, 91, 125, 130, 131, 138,
    139, 144

  Hair-tufts, 59, 123, 125, _129_, _158_

  Hairy grasses, _18_, 19, 21, 22, _23_, +26+, 57, 76, 81

  Hairy Brome--_Bromus asper_

  Hairy “seeds,” 168

  Half-shade species, 34

  Halophytes, 36

  Hard Fescue--_Festuca duriuscula_

  Hard-grass--_Lepturus_

  Hard leaves, 21, 47

  Hard Meadow-grass--_Poa rigida_

  Hardy Bamboos, 38

  Hare’s-tail--_Lagurus_

  Harsh leaves, 21

  Haulm, 83

  Havers--_Avena fatua_

  Hay, 27, 37

  Heath False-Brome--_Brachypodium pinnatum_

  Heath-grass--_Triodia decumbens_

  Heath-grasses, 20, +29+, 36

  Height, 6

  _Heleochloa_, 123

  Herbaceous--of the ordinary soft texture of herbs, 6, 21, 91

  _Heterodera_, 10

  Heterophylly, 71

  _Heteropogon contortus_, 127

  _Hierochloe_--Holy-grass, 20, 27, 66, 73, 91, 92, 105, 155;
    _H. borealis_, 30, 65

  Hill-pastures, 29

  Hispid--covered with stiff and rather long hairs, 58

  Histology, 62-71, 122

  _Holcus_--Soft grass, 8, 22, 26, 27, 56, 89, 90, 91, 93, +106+, 119,
    125, 148, 151, _152_, _153_, 155;
    _H. lanatus_, 7, 11, 13, 14, 17, _23_, 26, 28, 30, 32, 34, +59+,
      65, 69, +81+, +106+, 143, 151, +152+;
    _H. mollis_, 11, 28, 30, 33, 59, +106+, +153+

  Holy-grass--_Hierochloe_

  Hooded leaf-apex, 21

  Hook-hairs, 65

  _Hordeum_--Barley, 10, 20, 22, 26, 44, 59, 88, 89, 90, 92, +99+, 100,
    108, 127, 134, 163;
    _H. jubatum_, 125;
    _H. maritimum_, 8, 10, 29, 33, 59, +100+, +163+;
    _H. murinum_, 8, 10, 14, 21, 30, 50, +59+, +76+, +100+, 125, 162,
      +163+;
    _H. pratense_, 7, 11, 14, 21, 22, 28, +58+, +100+, +163+;
    _H. sylvaticum_, 7, 11, 14, 28, 34, 44, +58+, 59, +100+, 105, +162+

  Humus species, 33, 35

  Hybrids, 120

  Hydrophytes--plants requiring much water, and therefore aquatic or
    semi-aquatic, 37

  Hygrophilous species--hydrophytes, 70


  Imperfect--rudimentary or staminate, 105

  Inconspicuously awned grasses, 93

  Indicator-plants, 31, 32, 34

  Inflorescence, _5_, _9_, _12_, _15_, 83, +86+-+91+, 97, 99, 102, 103,
    105, 106, +109+-+118+, 119

  Infolding of leaves, 20, 23, 25, 62, +63+, 64

  Inrolling of leaves, 20, 23, 25, 46, 62, +63+, 64, _65_, _66_, _67_,
    _69_, 75, 78, 79, 80

  Intercellular spaces, 37

  Internode, 8, 17

  Intra-vaginal shoots, 12, 13

  Introduced grasses, 30

  Involute--rolled inwards, 20, 47

  Irritability of seedlings, 132

  Italian Rye-grass--_Lolium italicum_


  Keel, 18, _23_, 26, _63_, 68, 69, 91, 113, 127, 140, 144, 146, 147,
    148, 149, 151

  Keeled grasses, 26, 74

  _Knappia_--_Mibora_

  Kneed awns, _129_, 130, 151, 153, _154_, _158_

  Kneed stem, _9_

  Knot-grass--_Polygonum_

  _Kœleria_, 11, 14, 19, 20, 25, 26, 90, 91, 92, 101, 103, 110, 141,
    146, _149_;
    _K. cristata_, 8, 29, 32, 66, +81+, +109+, 148, +149+


  Lacunæ--air-spaces, 70, 73

  _Lagurus_--Hare’s-tail, 76, 88, 90, 92, 100, 101, 109;
    _L. ovatus_, 31

  Lamina--the blade of the leaf, 63-71, 95

  Lanceolate--narrow and tapering at both ends, 163

  Lanceolate-acuminate--lanceolate, but the upper end drawn out to a
    long point, 163

  Large grasses, 6

  Lawns, 10, 37

  Lax--loose, the spikelets on slender branches some distance apart,
    110, 117

  Layed shoots, 15

  Leaf, +17+-+27+, 39-61, 95, 133

  Leaf anatomy, 62-71, 72-82

  Leaf-apex, +21+

  Leaf-base, 10, 22, 40

  Leaf-blade--Lamina

  Leaf characters, 4, +20+-+27+

  Leaf-margin, +22+, 44, 66

  Leaf-section, _16_, 20, +62+-+72+

  Leaf-stalk--Petiole

  Leaf-surface, +22+, 65, 66, 67

  Least Quaking-grass--_Briza minor_

  Leathery leaves, 21

  _Leersia_--Cut-grass, 67, 70, 77, 90, 91, 92, 105, 120;
    _L. oryzoides_, 30, 66, 137

  Leguminosæ, 3

  _Lepturus_, 87, 90, 99;
    _L. filiformis_--_L. incurvatus_;
    _L. incurvatus_, 31

  Ligule, _18_, _19_, 45, 46, 51, 95, 113, 133

  Limestone species, 32

  Linear--at least five times as long as broad, with parallel straight
    sides, 19

  Linear-acuminate--linear, but tapering to a long point at the apex, 19

  Linear-acute--linear, but pointed at the apex, 39

  Linear-lanceolate--linear, but tapering at both ends, 19, 20, 163, 168

  Linear-oblong--oblong, but drawn out so that the sides are parallel
    for some distance, 16

  Local grasses, 30, 31

  Lodicules, 86, _87_, 95, _96_, 97

  _Lolium_--Rye-grass, 13, 14, 18, 22, 25, 49, 50, 53, 57, 59, 82, 88,
    90, 91, +107+, 108, 109, 144, 151, 167;
    _L. italicum_, 7, 11, 28, 31, +49+;
    _L. perenne_, 8, 11, 16, _19_, 20, 28, 30, 32, +49+, +81+, 82, 93,
      +107+, 128, 131, +142+, 143, 144, 150, 168;
    _L. temulentum_, 8, 10, 30, +49+, 50, 82, 92, +107+, _129_, 130,
      142, 150, 167, +168+

  Loose Panic-grass--_Panicum Crus-galli_

  _Lygeum_, 36

  Lyme-grass--_Elymus_


  Maize, 1, 89, 120

  Male flowers, 89, 90, 119

  Manna-croup--_Glyceria fluitans_

  Many-flowered spikelets, 90

  Margin of leaf, 21, +22+, 66

  Marginal asperities, 22

  Maritime grasses, 29

  Marram--_Psamma_

  Marsh Bent--_Agrostis alba_

  Marsh Foxtail--_Alopecurus geniculatus_

  Marsh grasses, 28, 29

  Mat-grass--_Psamma arenaria_

  Maydeæ, 122

  Meadows, 1

  Meadow Barley--_Hordeum pratense_

  Meadow Fescue--_Festuca elatior_--_Festuca pratensis_

  Meadow Foxtail--_Alopecurus pratensis_

  Meadow-grass--_Poa pratensis_, 83

  Meadow grasses, +27+, +28+, 37, 113

  Meadow Soft-grass--_Holcus lanatus_

  Mechanical tissues--tissues composed of hard-walled cells
    (sclerenchyma) serving for support, 62, _63_, _64_, 68

  Medium grasses, 7

  _Melica_--Melick, 11, 14, 16, 19, 20, 23, 25, 26, 34, 63, 90, 91, 92,
    110, +136+, 137, 142;
    _M. ciliata_, 32;
    _M. nutans_, 7, 17, 33, +41+, 78, 104, 105, +137+;
    _M. uniflora_, 7, 17, 28, 33, +40+, 41, 78, 104, +105+, 137

  _Melocanna_, 123

  Membranous ligule, 19

  Mesophytes--plants adapted to ordinary conditions of moisture, 37

  _Mibora_, 68, 87, 89;
    _M. verna_, 31, +74+, +99+

  Micropyle, _121_

  Microscopic characters, 62, 122

  Mid-rib, 15, 20, 21, 25, _63_, 67, 68, 74

  _Milium_--Millet-grass, 6, 11, 14, 20, 22, 27, 34, 89, 91, 92, 137;
    _M. effusum_, 6, 28, 33, +103+, +136+

  Millet--_Panicum_, 135

  Millet-grass--_Milium_

  Millet-seed type, 127, +135+

  Moist soils, 26, 32

  _Molinia_, 8, 14, 19, 20, 40, 60, 77, 90, 91, 92, 146, 148, 151, 171;
    _M. cærulea_, 7, 26, 29, 32, 33, 36, 37, 40, +59+, +110+, +148+,
      _149_

  Monocotyledons, 97, 134

  Monœcious--male and female flowers on the same plant, 119

  Moor-grass--_Sesleria_

  Moor-grasses, 8, 20, +29+, 37

  Moor Mat-grass--_Nardus stricta_, 83

  Morphology of flower, 95, 96, 97

  Morphology of spikelet, 94

  Motor-cells, 25, 41, 62, +63+, 64, _65_, _66_, _67_, _69_, 70, _71_,
    73, 74, 75, 76, 77, 78, 79, 80

  Mountain Melick--_Melica nutans_

  Movements of awns, 125, _126_, 127

  Movements of seedlings, 132

  Mucronate--with a short point suddenly springing from a rounded apex,
    22, 138, 139, 146, 149, _150_

  _Myosotis_, 3


  Naked fruits, 136

  _Nardus_, 8, _9_, 11, 14, 20, 21, 64, 65, 66, 67, 70, 80, 83, 87, 88,
    89, 90, 91, 93, 94, 130, 146, 171;
    _N. stricta_, 8, _9_, 29, 33, 36, +46+, 64, _69_, 70, +99+, 171,
      _173_, +174+

  Narrow-leafed Oat--_Avena pratensis_

  Narrow Small-reed--_Calamagrostis stricta_

  Naviculate--Boat-shaped, but pointed at both ends, 16

  Nematode worms, 10

  Nerves--minute veins on paleæ, 113, 115, _128_, _140_, 144, 168

  Nodes, 6, 8, 12, 14, 15

  Nodules, 10

  Northern Holy-grass--_Hierochloe borealis_

  Nucellus--the body of the ovule or young seed, _122_

  Nuclei, 121

  Numbers of grasses, 2


  Oat--_Avena_, 85, 89, +133+

  Oat-type of “seed,” 156

  Obsolete--so much reduced as to be practically absent, 19, 45, 48,
    115, 116

  Obtuse--rounded off and blunt at the apex, 19, 91

  Odours, 27

  Offsets, 12

  _Olyra_, 6

  One-flowered spikelets, 89

  One-glumed Fescue--_Festuca uniglumis_

  Open panicle--one where the primary branches stand off at right
    angles from the rachis, 112

  Orange spiked Foxtail--_Alopecurus fulvus_

  Orchids, 2

  Ovary, 86, _87_, 89, 95, _96_, 97, 119, 121

  Ovate-acute--egg-shaped in outline, but the free narrow end pointed, 61

  Ovate-lanceolate--ovate, but tapering above, 168


  Pale--Palea, 86, 89

  Palea, _84_, _85_, 86, _87_, +92+, _93_, 95, _96_, 97, 99-118, 119,
    120, _124_, 125, 127, _128_, _129_, 130, 131, 134, +135+-+174+

  Pampas-grass, 1

  Panic-grass--_Panicum_

  Panicle, _5_, _12_, 87, 88, 90, 91, 103, 105, 109-118

  _Panicum_, 4, 19, 67, 69, 72, 87, 90, 92, 101, 105, 109, 124, 135,
    136, 137, 142;
    _P. Crus-galli_, 137;
    _P. glaucum_, 30;
    _P. plicatum_, 21;
    _P. sanguinale_, 30;
    _P. verticillatum_, 30

  Papillæ--protruding cells not long enough to be termed hairs, 64, 67

  Pappus, 125

  Parallel venation, 21, 22

  Parenchyma--ordinary soft cellular tissue of herbaceous parts, 64, 65

  Partial inflorescence, 86

  Pasture, 1, 10

  Pasture-grasses, +27+, +28+, 37

  Perennial Beard-grass--_Polypogon littoralis_

  Perennial grasses, 10, 11, 40, 43, 58, 114

  Perennial Oat--_Avena pratensis_

  Perennial Oat-grass--_Avena pratensis_

  Perfect flowers, 89, 90, 99, 100, 105, 106

  Perianth--the floral coverings, 96

  Pericarp--the coats of the true fruit, _121_, _122_

  Petiole, 5, 17

  _Phalaris_--Canary grass, 88, 101, 109, 136;
    _P. arundinacea_--_Digraphis arundinacea_;
    _P. canariensis_, 31, 139

  _Phleum_, 66, 88, 89, 90, 91, 93, +102+, 109, 110, 136, 137, 142;
    _P. alpinum_, 30, 102;
    _P. arenarium_, 7, 10, 29, 37, +55+, +102+, 136;
    _P. asperum_, 31, 55, 102, 136;
    _P. Bœhmeri_, 8, 31, 55, 102, 136;
    _P. nodosum_--var. of _P. pratense_;
    _P. phalaroides_--_P. Bœhmeri_;
    _P. pratense_, 7, 8, 11, 13, 25, 28, 32, +55+, 70, +76+, +102+,
      _128_, +135+

  Phloem, 67

  _Phragmites communis_--_Arundo Phragmites_

  Physiognomy, 36, 37

  Piercing of soil, 132

  Pilose--with scattered, rather long soft hairs, 59

  Plaited vernation, 21

  _Plantago_, 3

  Plicate--plaited

  Plume-like inflorescence, 91, 103

  Plumule, _121_, 123, 132, 133

  _Poa_, 2, 15, 20, 21, 23, 25, 26, 47, 54, 61, 74, 83, 84, 88, 89, 90,
    91, 92, 103, 104, 109, 110, +113+, 114, 115, 116, 118, 127, 131, 140,
    141, 144, 146, 151, 162;
    _P. alpina_, 8, 11, 13, 14, 16, 17, 31, +44+, 54, 63, 114, 134,
      +146+;
    _P. annua_, 8, 10, 14, 16, 30, 34, 42, +53+, 54, _63_, 68, 74, 75,
      +114+, _127_, 141, +146+;
    _P. aquatica_--_Glyceria aquatica_;
    _P. bulbosa_, 8, 11, 14, 29, +54+, 69, 111, 114, 146;
    _P. compressa_, 8, 11, 14, 15, 16, 30, 32, 42, +53+, 54, 63, 69,
      74, 111, +114+, 139, +140+;
    _P. distans_, 29, 30, 114, 146;
    _P. fertilis_--_P. serotina_, 45;
    _P. fluitans_--_Glyceria fluitans_;
    _P. laxa_, 31, 134;
    _P. loliacea_, 31, 108, 114, 146;
    _P. maritima_, 8, 11, 14, 16, 20, 22, 26, 29, +47+, 54, +111+, 114,
      146;
    _P. nemoralis_, 7, 11, 14, 15, 28, 34, 45, +54+, 63, 74, 75, 113,
      +114+, 139, _140_, +141+, 161;
    _P. pratensis_, 7, 11, 13, 14, 16, 17, 27, 32, 33, 41, 42, +44+,
      45, 54, 55, 67, 75, 113, +114+, 139, +140+, 141;
    _P. procumbens_, 31, 111, 114;
    _P. rigida_, 10, 14, 30, +111+, 114, 146;
    _P. stricta_--var.of _P. alpina_, 134;
    _P. trivialis_, 7, 11, 13, 14, 16, 17, _18_, 27, 32, +42+, 44, 45,
      54, +74+, 90, 112, +113+, 139, _140_, +141+, 146, 148

  Pollen, _93_, 94, 119

  Pollen-grain, _120_, +121+

  Pollen-tube, _120_, +121+

  Pollination, _93_, 119, +120+, +121+

  _Polygonum_, 3

  _Polypogon_--Beard-grass, 69, 90, 91, 92, 100, 101, 109;
    _P. littoralis_, 31;
    _P. monspeliensis_, 31

  Ponds, grasses of, 28, 29

  Popular names, 6

  Potassium salts, 32

  Prairies, 1, 36, 38

  Prickle-hairs, 66

  Primary root, 123, 131

  Procumbent Meadow-grass--_Poa procumbens_

  Protandrous--when the pollen is mature and shed before the stigma of
    the same flower is ready for pollination, 119

  Proterogynous--when the stigma is receptive before the pollen of the
    same flower is mature, 119

  _Psamma_, 4, 11, 13, 14, 21, 25, 36, 48, 79, 81, 89, 90, 92, 95, 138;
    _P. arenaria_, 7, 29, 33, 35, 36, +48+, 70, +79+, +102+, 138, +139+

  Pubescence--hairiness, 26

  Pungent--spine-like, 22

  Purple-flowered Small-reed--_Calamagrostis lanceolata_

  Purple-stalked Cat’s-tail--_Phleum Bœhmeri_

  Purple-veined sheaths, 18


  Quadrangular shoot-section, 16, 40

  Quake-grass--_Briza_

  Quaking-grass--_Briza media_


  Racemous--like a raceme, 105

  Rachilla, 85, _123_, _124_, _128_, _129_, 131, _137_, 138, 142,
    _143_, 144, _149_, _150_, _164_, _167_, _169_, _170_, _172_

  Rachis, _9_, 85, 88, 106, 107

  Radicle, _121_, 123

  Rare grasses, 6, +30+, +31+, 89, 90, 91, 92

  Rat’s-tail Fescue--_Festuca Myurus_

  Red-sheathed grasses, 18, 49, 59

  Reed, 2

  Reed Canary grass--_Digraphis arundinacea_

  Reed Fescue--_Festuca sylvatica_

  Reed-grass, 1, 6

  Reed Meadow-grass--_Glyceria aquatica_

  Reed Sweet-grass--_Glyceria aquatica_

  Reflexed leaves, _16_

  Reflexed Meadow-grass--_Poa distans_

  Rhizomes, 10, 11, 35, 36, 37

  Rhomboidal shoot-section, 16, 42

  Rib-grass--_Plantago_

  Ribbon-grass--_Digraphis arundinacea_

  Ribs--the more opaque veins due to the larger vascular-bundles, 22,
    25, 62, 91, _127_

  Rice, 1

  Ridgeless grasses, 25

  Ridges, _18_, 21, 22, +23+, _24_, +25+, 26, 47, 51, 53, 54, _65_,
    _66_, _67_, 68, _69_, _71_, 73, 77, 78, 79, 80, 91

  River-banks, 28, 29

  Road-sides, 29

  Rolled leaves, 15, _16_, 20, 24, 25, 63

  Rolling of leaves, 24, 25, 36

  Root-cap, _121_

  Roots, 8, 12, 35, _121_, 123, 131, 132, 133

  Rough Cock’s-foot--_Dactylis glomerata_

  Rough Meadow-grass--_Poa trivialis_

  Rough Phleum--_Phleum asperum_

  Rough-stalked Meadow-grass--_Poa trivialis_

  Round shoots, 15, _16_, 42, 50, 57

  Ruderal grasses, 29, 32, 34, 35

  Rudimentary flowers, 89, 90, 105

  Runners, 12, 13, 14

  Rushes, 4, 33

  Rushy Wheat-grass--_Agropyrum junceum_

  Rye--_Secale_, 120, 132, +133+

  Rye Brome--_Bromus secalinus_

  Rye-grass--_Lolium perenne_


  Salt species, 33

  Sand-binders, 13, 35, 36, 48, 102, 107, 108

  Sand Cat’s-tail--_Phleum arenarium_

  Sand dunes, 35, 36

  Sand species, 29, 32, 36

  Sandy situations, 8, 29, 33

  Savannahs, 1, 38

  Scaberulous--slightly rough to the touch, 22, 45, 164

  Scabrid--rough to the touch, 22, 47, 54

  Scarious--as if scorched by fire, 92, 145

  Scents, 27

  Sclerenchyma--mechanical tissue, 62, _65_, _66_, _67_, +68+, _69_,
    70, _71_, 74, 75, 76, 79, 80

  _Sclerochloa_--_Poa_

  _Sclerochloa maritima_--_Poa maritima_;
    _S. procumbens_--_Poa procumbens_;
    _S. rigida_--_Poa rigida_

  Scorpion-grass--_Myosotis_

  Scutellum, _121_, 123

  Sea Barley--_Hordeum maritimum_

  Sea Cat’s-tail--_Phleum arenarium_

  Sea-grass--_Zostera_

  Sea Hard-grass--_Lepturus incurvatus_

  Sea Lyme-grass--_Elymus arenarius_

  Sea Mat-grass--_Psamma arenaria_

  Sea Mat-weed--_Psamma arenaria_

  Sea Meadow-grass--_Poa maritima_

  Sea Poa--_Poa maritima_

  Sea Reed--_Psamma arenaria_

  Sea-side grasses, 27, 29

  Secondary roots, _121_, 123, 131, 133

  Secund--turned to one side, _9_, 89, 108, 109, 114

  Sedges, 3, 4, 33, 35, 121

  Seed--strictly the contents of the caryopsis (fruit), but in practice
    the fruit and its adherent paleæ etc. (chaff) are termed “seed,”
    119, 120, 121, 123, +124+, 125, _127_, 128, 129, 130, _131_, +134+,
    +135+-+174+

  Seed-coats, 121, _122_

  Seedlings, 132, +133+

  Semi-aquatic species, 28, 29

  Separation of fruits, _124_

  Serrulæ--minute tooth-like asperities, 22, 91, _173_

  _Sesleria_--Moor-grass, 22, 25, 63, 64, 68, 90, 91, 93, 101;
    _S. cærulea_, 17, +42+, 67, +108+, 149, +151+

  Sessile--sitting directly on an axis without an intervening stalk,
    87, 99, 107

  Setaceous--bristle-like, _16_, 19, 20, 21, _24_, 45, 111, 113

  _Setaria_--_Panicum_

  Sexual organs, 134

  Shade action of grasses, 35

  Shade-grasses, 20, +28+, 33, 34, 70

  Shapes of caryopsis, 127

  Shapes of leaves, 4, 19, 20

  Shapes of shoot, 16

  Sharp-edged shoots, 16

  Sheath, 5, 8, 12, 15, _16_, 17, _18_, _19_, 20, 22, 51, 95, 133

  Sheep’s Fescue--_Festuca ovina_

  Shelving sheath-margin, 22

  Shoot, 10, 12, 15, 16, 123

  _Sieglingia decumbens_--_Triodia decumbens_

  Siliceous--impregnated with flint--silex, 64, 65, 66

  Silky Bent-grass--_Agrostis Spicaventi_

  Silvery Hair-grass--_Aira caryophyllea_

  Single-husked Fescue--_Festuca uniglumis_

  Slender Foxtail--_Alopecurus agrestis_

  Small grasses, 7

  Small Reed--_Calamagrostis_

  Smooth Brome--_Bromus racemosus_

  Sociable plants, 36

  Sod, 37

  Sodium chloride, 33

  Soft Brome--_Bromus mollis_

  Soft-grass--_Holcus_

  Soft Holcus--_Holcus mollis_

  Soil formation, 36

  Soil protection, 36

  Solid leaves, 46

  Solid stems, 4

  Sour soils, 33

  _Spartina_--Cord-grass, 69, 87, 90, 99, 105;
    _S. stricta_, 27, 31, 78

  Spear, 123, 132

  Spikate inflorescence, 99, 106

  Spike, _9_, 87, 88, 90, 99, 100, 101, 102, 106, 108

  Spiked Fescue--_Festuca loliacea_

  Spikelet, 9, _84_, _85_, +86+, _87_, 88, +89+, +90+, _93_, _94_, 95,
    97, 99-118, 119, 120, 123, _124_

  Spike-like panicle, _9_, 88, 90, 102

  Spinescent leaf, 22

  _Spinifex_, 125

  Split sheath, 5, 17, _18_, _19_

  Split-sheathed grasses, 17, _18_, _19_, 45, 50

  _Sporobolus_, 123, 134

  Squirrel-tail grass--_Hordeum maritimum_

  Stamen, 86, _87_, 89, _93_, 94, 95, _96_, 97, 102, 103, 119

  Staminate--a flower with stamens and no ovary, 100, 105, 106

  Starch, 120, 121, 122

  Stem, 4, 6, 8

  Steppes, 1, 36, 38

  Stigma--stigmatic plumes, 86, _87_, _93_, 94, 96, 97, +119+, _120_, 121

  _Stipa_, 36, 96, _126_;
    _S. capillata_, 125;
    _S. pennata_, 32, 125;
    _S. spartea_, 125

  Stolon, 10, 12, 35, 114

  Stoloniferous grasses, 8, 13, 14, _15_

  Stomata, 25, 36, 62, 64, 65, 67, 70, 73, 77, 80, 95

  Strand-plants, 36

  Stringy roots, 8

  Striped grass--_Digraphis arundinacea_

  Struggle for existence, 2, 37, 38

  Style, 94, 97, 99

  Sub-acute--hardly pointed, 142

  Sub-sessile--very shortly stalked, so as to be all but sessile, 99,
    106

  Sub-terminal awn, 95, 115, _129_, 130, _150_, 151, _152_, 162,
    163-168, _169_

  Subulate--awl-shaped: stouter than setaceous, 19, 20, 21, 70, _71_, 79

  Sugar, 120, 121, 122

  Sugar-cane, 1

  Sun-plants, 36

  Sweet-tasting grasses, 39

  Sweet Vernal grass--_Anthoxanthum odoratum_

  Sympodium, 11


  Tall Brome--_Bromus giganteus_

  Tall Fescue--_Festuca elatior_

  Tapering leaves, 21

  Tastes, 27

  Temperate species, 2

  Terete--cylindrical and gradually tapering, 6, 54, 163, 171

  Terminal awn, 92, 111, 115, 116, _126_, +130+, 162, 168-174, _173_

  Texture of leaf, +21+

  Three-flowered spikelets, 90

  Timothy--_Phleum pratense_

  Tomentose--softly hairy, 59

  Transpiration, 20

  Transverse sections of leaves, _16_, _23_, _24_, _63_, _64_

  Transverse section of shoot, 15, 16

  _Triodia_--Heath-grass, 11, 14, 19, 25, 26, 90, 91, 103, 139;
    _T. decumbens_, 8, 29, 34, +110+, _123_

  _Trisetum flavescens_--_Avena flavescens_

  _Triticum_--Wheat;
    _T. acutum_--_T. laxum_;
    _T. junceum_--_Agropyrum junceum_;
    _T. laxum_--_Agropyrum laxum_;
    _T. pungens_--_T. laxum;_
    _T. repens_--_Agropyrum repens_

  Tropical species, 1, 2

  Truncate, 92, 142

  Tuber, 8

  Tufted grasses, 13, 14

  Tufted Hair-grass--_Aira cæspitosa_

  Tufted inflorescences, 90, 99, 102, 103, 109

  Tufts, _5_, _9_, 12, 13, 37

  Tumble-weeds, 125

  Turgescence--the distension of cells with water which they have
    absorbed, 63

  Tussocks, 13

  Twisted awns, 116, 125, _126_, _129_, 130, 151, 154, _158_

  Twisting of seedling leaves, 133

  Twitch--certain persistent weeds belonging to the genera _Agropyrum_,
    _Agrostis_, _Holcus_, etc.: _see_ Couch-grass, 52, 57, 59

  Two-flowered spikelets, 90


  +U+-shaped leaf-sections, 20

  _Uniola_, 97

  Upright Brome--_Bromus erectus_.
    Also _B. madritensis_

  Uses of grasses, 1, 2


  +V+-shaped leaf-sections, 20, 53, 73

  Vagabond grasses, 29, 32, 34

  Variability, 26

  Vascular bundles, 21, 22, 62, _63_, _64_, _65_, _66_, _67_, +68+,
    _69_, 70, _71_, 75, 76, 78, 80, 81

  Vascular-bundle sheath, 68, 95, _122_

  Vegetative organs, 4

  Veins, 18, 21, 22, 68, 76, 91

  Venation, +21+, 62, +67+, 68

  Vermin, 35

  Vernal grass--_Anthoxanthum_, 83

  Vernation--folding of the leaves in bud, 21

  Versatile--hung loosely so as to turn freely, 94

  Vessels, 67

  Violet-brown sheath, 18

  Viviparous grasses, 112, 114, 134

  _Vulpia Myurus_--_Festuca Myurus_;
    _V. uniglumis_--_Festuca uniglumis_


  Wall Barley--_Hordeum murinum_

  Wall Fescue--_Festuca Myurus_

  Walls, grasses of, 29

  Waste-places, 29

  Water-storing tissues, 36, 70

  Water Whorl-grass--_Catabrosa aquatica_

  Wavy Hair-grass--_Aira flexuosa_

  Wavy Meadow-grass--_Poa laxa_

  Wax, 36, 70

  Web--minute tufted soft hairs at the base of the caryopsis, 113, 114,
    _127_, 131, 138, 139, _140_, 141

  Weeds, 27, 28, 29, 35

  Wheat--_Triticum_, 1, 120, 127, 132, +133+

  Wheat-grass--_Agropyrum_

  Whorl-grass--_Catabrosa_

  Wild Oat--_Avena fatua_, 117

  Wind-borne seeds, 125, _126_

  Wings, 125, 142

  Wood Barley--_Hordeum sylvaticum_

  Wood False-Brome--_Brachypodium sylvaticum_

  Wood Meadow-grass--_Poa nemoralis_

  Wood Melick--_Melica uniflora_

  Wood Poa--_Poa nemoralis_

  Wood-species, +28+, 33

  Woolly Holcus--_Holcus lanatus_


  Xenia--cases where the direct influence of the pollen is evident on
    the seed resulting from its action, 120

  Xerophilous--of the nature of a xerophyte, 70

  Xerophytes--plants adapted to dry situations, 24, 25, 36, 37, 38, 68, 70

  Xylem, 67


  Yellow Oat-grass--_Avena flavescens_

  Yellow-sheathed grasses, 18

  Yorkshire Fog--_Holcus lanatus_, 152


  _Zostera_, 3


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At the same time it is expressed in language so clear and devoid of
technicalities that the amateur who wishes to know something about
our trees and shrubs will find this one of the most useful guides to
which he can turn.... The work is a many sided one, acting not only
as a guide to the naturalist in the field, but also as a laboratory
handbook, where the use of the lens and microscope may be employed
to amplify the study of objects already observed in their natural
habitats. Botanists generally, and especially forest botanists will
welcome the appearance of this book as supplying a decided want, and
filling a distinct gap in our literature of forest botany.


  +Grasses+: a Handbook for use in the Field and Laboratory. By H.
    MARSHALL WARD, Sc.D., F.R.S. Crown 8vo. With 81 figures. 6_s._

_Field._ The work is essentially suited to the requirements of those
desirous of studying the grasses commonly grown in this country, and it
can fairly be said that it furnishes an amount of information seldom
obtained in more pretentious volumes.

  P. T. O.


  +A Treatise on the British Freshwater Algæ.+ By G. S. WEST, M.A.,
    A.R.C.S., F.L.S., Lecturer in Botany in the University of Birmingham.
    Demy 8vo. With a frontispiece and 166 illustrations. 10_s._ 6_d._
    _net_.

_Nature._ Its aim is stated as “to give the student a concise account
of the structure, habits and life-histories of Freshwater Algæ, and
also to enable him to place within the prescribed limits of a genus
any Algæ he may find in the freshwater of the British Islands.” To do
this within the limits of an octavo volume of less than 400 pages, in
which are numerous illustrations, is a task possible of accomplishment
only by one very familiar with the subject and skilled in concise
expression; but that it has been successfully done will, we think,
be the verdict after testing the book thoroughly.... Prof. West’s
treatment of his subject is instructive and stimulating.

  +A Manual and Dictionary of the Flowering Plants and Ferns.+ By J. C.
    WILLIS, M.A., Sc.D., Director of the Royal Botanic Gardens, Ceylon.
    _Third edition._ Crown 8vo. 10_s._ 6_d._

_Field._ Taking this handy volume and a local flora, the traveller
or student may do an enormous amount of practical field work without
any other botanical literature whatever.... The result is a work that
ought to be included in every library of botany and horticulture or
agriculture, and it is certainly one that the nomadic botanist cannot
afford to leave at home.... We have used the original edition of this
work since its publication, and have found it to be one of the most
useful and comprehensive works on plants ever produced.

_Athenæum._ The whole is well abreast of modern research, and a
thoroughly business-like volume, lucid though compact.


  +Agriculture in the Tropics.+ An elementary Treatise. By J. C.
    WILLIS, M.A., Sc.D. Demy 8vo. With 25 plates. 7_s._ 6_d. net_.


  +Palæontology--Invertebrate.+ By HENRY WOODS, M.A., F.G.S.,
    University Lecturer in Palæozoology. _Fourth edition._ Crown 8vo.
    With 151 illustrations. 6_s._


  +Outlines of Vertebrate Palæontology for students of Zoology.+ By
    ARTHUR SMITH WOODWARD, M.A., F.R.S., Keeper of the Department of
    Geology in the British Museum. Demy 8vo. With 228 illustrations.
    14_s._

_Athenæum._ The author is to be congratulated on having produced a work
of exceptional value, dealing with a difficult subject in a thoroughly
sound manner.


  CAMBRIDGE UNIVERSITY PRESS
  London: FETTER LANE, E.C.
  C. F. CLAY, MANAGER
  Edinburgh: 100, Princes Street
  ALSO
  London: H. K. Lewis, 136, Gower Street, W.C.





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