Chapter II: CLASSIFICATION.--Gramineae are sharply defined from all other

plants, and there are no genera as to which it is possible to feel a doubt whether they should be referred to it or not. The only family closely allied is Cyperaceae, and the points of difference between the two may be here brought together. The best distinctions are found in the position of the embryo in relation to the endosperm--lateral in grasses, basal in Cyperaceae--and in the possession by Gramineae of the 2-nerved palea below each flower. Less absolute characters, but generally trustworthy and more easily observed, are the feathery stigmas, the always distichous arrangement of the glumes, the usual absence of more general bracts in the inflorescence, the split leaf-sheaths, and the hollow, cylindrical, jointed culms--some or all of which are wanting in all Cyperaceae. The same characters will distinguish grasses from the other glumiferous orders, Restiaceae, and Eriocaulonaceae, which are besides further removed by their capsular fruit and pendulous ovules. To other monocotyledonous families the resemblances are merely of adaptive or vegetative characters. Some Commelinaceae and Marantaceae approach grasses in foliage; the leaves of _Allium_, &c., possess a ligule; the habit of some palms reminds one of the bamboos; and Juncaceae and a few Liliaceae possess an inconspicuous scarious perianth. There are about 300 genera containing about 3500 well-defined species.

The great uniformity among the very numerous species of this vast family renders its _classification_ very difficult. The difficulty has been increased by the confusion resulting from the multiplication of genera founded on slight characters, and from the description (in consequence of their wide distribution) of identical plants under several different genera.

No characters for main divisions can be obtained from the flower proper or fruit (with the exception of the character of the hilum), and it has therefore been found necessary to trust to characters derived from the usually less important inflorescence and bracts.

Robert Brown suggested two primary divisions--Paniceae and Poaceae, according to the position of the most perfect flower in the spikelet; this is the upper (apparently) terminal one in the first, whilst in the second it occupies the lower position, the more imperfect ones (if any) being above it. Munro supplemented this by another character easier of verification, and of even greater constancy, in the articulation of the pedicel in the Paniceae immediately below the glumes; whilst in Poaceae this does not occur, but the axis of the spikelet frequently articulates _above_ the pair of empty basal glumes. Neither of these great divisions will well accommodate certain genera allied to _Phalaris_, for which Brown proposed tentatively a third group (since named _Phalarideae_); this, or at least the greater part of it, is placed by Bentham under the Poaceae.

The following arrangement has been proposed by Professor Eduard Hackel in his recent monograph on the order.

A. Spikelets one-flowered, rarely two-flowered as in Zea, falling from
the pedicel entire or with certain joints of the rachis at maturity.
Rachilla not produced beyond the flowers.

a. Hilum a point; spikelets not laterally compressed.

[alpha] Fertile glume and pale hyaline; empty glumes thick,
membranous to coriaceous or cartilaginous, the lowest the largest.
Rachis generally jointed and breaking up when mature.

1. Spikelets unisexual, male and female in separate inflorescences
or on different parts of the same inflorescence.
1. _Maydeae_.

2. Spikelets bisexual, or male and bisexual, each male standing
close to a bisexual.
2. _Andropogoneae_.

[beta] Fertile glume and pale cartilaginous, coriaceous or papery;
empty glumes more delicate, usually herbaceous, the lowest usually
smallest. Spikelets falling singly from the unjointed rachis of the
spike or the ultimate branches of the panicle.
3. _Paniceae_.

b. Hilum a line; spikelets laterally compressed.
4. _Oryzeae_.

B. Spikelets one- to indefinite-flowered; in the one-flowered the
rachilla frequently produced beyond the flower; rachilla generally
jointed above the empty glumes, which remain after the fruiting glumes
have fallen. When more than one-flowered, distinct internodes are
developed between the flowers.

a. Culm herbaceous, annual; leaf-blade sessile, and not jointed to the
sheath.

[alpha] Spikelets upon distinct pedicels and arranged in panicles or
racemes.

I. Spikelets one-flowered.

i. Empty glumes 4. 5. _Phalarideae_.
ii. Empty glumes 2. 6. _Agrostideae_.

II. Spikelets more than one-flowered.

i. Fertile glumes generally shorter than the empty glumes, usually
with a bent awn on the back.
7. _Aveneae_.

ii. Fertile glumes generally longer than the empty, unawned or
with a straight, terminal awn.
9. _Festuceae_.

[beta] Spikelets crowded in two close rows, forming a one-sided
spike or raceme with a continuous (not jointed) rachis.
8. _Chlorideae_.

[gamma] Spikelets in two opposite rows forming an equal-sided spike.
10. _Hordeae_.

b. Culm woody, at any rate at the base, leaf-blade jointed to the
sheath, often with a short, slender petiole.
11. _Bambuseae_.

Tribe 1. _Maydeae_ (7 genera in the warmer parts of the earth). _Zea
Mays_ (maize, q.v., or Indian corn) (q.v.). _Tripsacum_, 2 or 3
species in subtropical America north of the equator; _Tr. dactyloides_
(gama grass) extends northwards to Illinois and Connecticut; it is
used for fodder and as an ornamental plant. _Coix Lacryma-Jobi_ (Job's
tears) q.v.

Tribe 2. _Andropogoneae_ (25 genera, mainly tropical). The spikelets
are arranged in spike-like racemes, generally in pairs consisting of a
sessile and stalked spikelet at each joint of the rachis (fig. 18).
Many are savanna grasses, in various parts of the tropics, for
instance the large genus _Andropogon_, _Elionurus_ and others.
_Saccharum officinarum_ (sugar-cane) (q.v.). _Sorghum_, an important
tropical cereal known as black millet or _durra_ (q.v.). _Miscanthus_
and _Erianthus_, nearly allied to _Saccharum_, are tall reed-like
grasses, with large silky flower-panicles, which are grown for
ornament. _Imperata_, another ally, is a widespread tropical genus;
one species _I. arundinacea_ is the principal grass of the alang-alang
fields in the Malay Archipelago; it is used for thatch. _Vossia_, an
aquatic grass, often floating, is found in western India and tropical
Africa. In the swampy lands of the upper Nile it forms, along with a
species of _Saccharum_, huge floating grass barriers. _Elionurus_, a
widespread savanna grass in tropical and subtropical America, and also
in the tropics of the old world, is rejected by cattle probably on
account of its aromatic character, the spikelets having a strong
balsam-like smell. Other aromatic members are _Andropogon Nardus_, a
native of India, but also cultivated, the rhizome, leaves and
especially the spikelets of which contain a volatile oil, which on
distillation yields the citronella oil of commerce. A closely allied
species, _A. Schoenanthus_ (lemon-grass), yields lemon-grass oil; a
variety is used by the negroes in western Africa for haemorrhage.
Other species of the same genus are used as stimulants and cosmetics
in various parts of the tropics. The species of _Heteropogon_, a
cosmopolitan genus in the warmer parts of the world, have strongly
awned spikelets. _Themeda Forskalii_, which occurs from the
Mediterranean region to South Africa and Tasmania, is the kangaroo
grass of Australia, where, as in South Africa, it often covers wide
tracts.

Tribe 3. _Paniceae_ (about 25 genera, tropical to subtropical; a few
temperate), a second flower, generally male, rarely hermaphrodite, is
often present below the fertile flower. _Paspalum_, is a large
tropical genus, most abundant in America, especially on the pampas and
campos; many species are good forage plants, and the grain is
sometimes used for food. _Amphicarpum_, native in the south-eastern
United States, has fertile cleistogamous spikelets on filiform runners
at the base of the culm, those on the terminal panicle are sterile.
_Panicum_, a very polymorphic genus, and one of the largest in the
order, is widely spread in all warm countries; together with species
of _Paspalum_ they form good forage grasses in the South American
savannas and campos. _Panicum Crus-galli_ is a polymorphic
cosmopolitan grass, which is often grown for fodder; in one form (_P.
frumentaceum_) it is cultivated in India for its grain. _P. plicatum_,
with broad folded leaves, is an ornamental greenhouse grass. _P.
miliaceum_ is millet (q.v.), and _P. altissimum_, Guinea grass. In the
closely allied genus _Digitaria_, which is sometimes regarded as a
section of _Panicum_, the lowest barren glume is reduced to a point;
_D. sanguinalis_ is a very widespread grass, in Bohemia it is
cultivated as a food-grain; it is also the crab-grass of the southern
United States, where it is used for fodder.

In _Setaria_ and allied genera the spikelet is subtended by an
involucre of bristles or spines which represent sterile branches of
the inflorescence. _Setaria italica_, Hungarian grass, is extensively
grown as a food-grain both in China and Japan, parts of India and
western Asia, as well as in Europe, where its culture dates from
prehistoric times; it is found in considerable quantity in the lake
dwellings of the Stone age.

In _Cenchrus_ the bristles unite to form a tough spiny capsule (fig.
12); _C. tribuloides_ (bur-grass) and other species are troublesome
weeds in North and South America, as the involucre clings to the wool
of sheep and is removed with great difficulty. _Pennisetum typhoideum_
is widely cultivated as a grain in tropical Africa. _Spinifex_, a
dioecious grass, is widespread on the coasts of Australia and eastern
Asia, forming an important sand-binder. The female heads are spinose
with long pungent bracts, fall entire when ripe and are carried away
by wind or sea, becoming finally anchored in the sand and falling to
pieces.

Tribe 4. _Oryzeae_ (16 genera, mainly tropical and subtropical). The
spikelets are sometimes unisexual, and there are often six stamens.
_Leersia_ is a genus of swamp grasses, one of which _L. oryzoides_
occurs in the north temperate zone of both old and new worlds, and is
a rare grass in Surrey, Sussex and Hampshire. _Zizania aquatica_
(Tuscarora or Indian rice) is a reed-like grass growing over large
areas on banks of streams and lakes in North America and north-east
Asia. The Indians collect the grain for food. _Oryza sativa_ (rice)
(q.v.). _Lygeum Spartum_, with a creeping stem and stiff rush-like
leaves, is common on rocky soil on the high plains bordering the
western Mediterranean, and is one of the sources of esparto.

Tribe 5. _Phalarideae_ (6 genera, three of which are South African and
Australasian; the others are more widely distributed, and represented
in our flora). _Phalaris arundinacea_, is a reed-grass found on the
banks of British rivers and lakes; a variety with striped leaves known
as ribbon-grass is grown for ornament. _P. canariensis_ (Canary grass,
a native of southern Europe and the Mediterranean area) is grown for
bird-food and sometimes as a cereal. _Anthoxanthum odoratum_, the
sweet vernal grass of our flora, owes its scent to the presence of
coumarin, which is also present in the closely allied genus
_Hierochloe_ (fig. 19), which occurs throughout the temperate and
frigid zones.

Tribe 6. _Agrostideae_ (about 35 genera, occurring in all parts of the
world; eleven are British). _Aristida_ and _Stipa_ are large and
widely distributed genera, occurring especially on open plains and
steppes; the conspicuously awned persistent flowering glume forms an
efficient means of dispersing the grain. _Stipa pennata_ is a
characteristic species of the Russian steppes. _St. spartea_
(porcupine grass) and other species are plentiful on the North
American prairies. _St. tenacissima_ is the Spanish esparto grass
(q.v.), known in North Africa as halfa or alfa. _Phleum_ has a
cylindrical spike-like inflorescence; _P. pratense_ (timothy) is a
valuable fodder grass, as also is _Alopecurus pratensis_ (foxtail).
_Sporobolus_, a large genus in the warmer parts of both hemispheres,
but chiefly America, derives its name from the fact that the seed is
ultimately expelled from the fruit. _Agrostis_ is a large world-wide
genus, but especially developed in the north temperate zone, where it
includes important meadow-grasses. _Calamagrostis_ and _Deyeuxia_ are
tall, often reed-like grasses, occurring throughout the temperate and
arctic zones and upon high mountains in the tropics. _Ammophila
arundinacea_ (or _Psamma arenaria_) (Marram grass) with its long
creeping stems forms a useful sand-binder on the coasts of Europe,
North Africa and the Atlantic states of America.

Tribe 7. _Aveneae_ (about 24 genera, seven of which are British).
_Holcus lanatus_ (Yorkshire fog, soft grass) is a common meadow and
wayside grass with woolly or downy leaves. _Aira_ is a genus of
delicate annuals with slender hair-like branches of the panicle.
_Deschampsia_ and _Trisetum_ occur in temperate and cold regions or on
high mountains in the tropics; _T. pratense_ (_Avena flavescens_) with
a loose panicle and yellow shining spikelets is a valuable
fodder-grass. _Avena fatua_ is the wild oat and _A. sativa_ the
cultivated oat (q.v.). _Arrhenatherum avenaceum_, a perennial field
grass, native in Britain and central and southern Europe, is
cultivated in North America.

Tribe 8. _Chlorideae_ (about 30 genera, chiefly in warm countries).
The only British representative is _Cynodon Dactylon_ (dog's tooth,
Bermuda grass) found on sandy shores in the south-west of England; it
is a cosmopolitan, covering the ground in sandy soils, and forming an
important forage grass in many dry climates (Bermuda grass of the
southern United States, and known as durba, dub and other names in
India). Species of _Chloris_ are grown as ornamental grasses.
_Bouteloua_ with numerous species (mesquite grass, grama grass) on the
plains of the south-western United States, afford good grazing.
_Eleusine indica_ is a common tropical weed; the nearly allied species
_E. Coracana_ is a cultivated grain in the warmer parts of Asia and
throughout Africa. _Buchloe dactyloides_ is the buffalo grass of the
North American prairies, a valuable fodder.

Tribe 9. _Festuceae_ (about 83 genera, including tropical, temperate,
arctic and alpine forms) many are important meadow-grasses; 15 are
British. _Gynerium argenteum_ (pampas grass) is a native of southern
Brazil and Argentina. _Arundo_ and _Phragmites_ are tall reed-grasses
(see REED). Several species of _Triodia_ cover large areas of the
interior of Australia, and from their stiff, sharply pointed leaves
are very troublesome. _Eragrostis_, one of the larger genera of the
order, is widely distributed in the warmer parts of the earth; many
species are grown for ornament and _E. abyssinica_ is an important
food-plant in Abyssinia. _Koeleria cristata_ is a fodder-grass. _Briza
media_ (quaking grass) is a useful meadow-grass. _Dactylis glomerata_
(cock's-foot), a perennial grass with a dense panicle, common in
pastures and waste places is a useful meadow-grass. It has become
naturalized in North America, where it is known as orchard grass, as
it will grow in shade. _Cynosurus cristatus_ (dog's tail) is a common
pasture-grass. _Poa_, a large genus widely distributed in temperate
and cold countries, includes many meadow and alpine grasses; eight
species are British; _P. annua_ (fig. 20) is the very common weed in
paths and waste places; _P. pratensis_ and _P. trivialis_ are also
common grasses of meadows, banks and pastures, the former is the "June
grass" or "Kentucky blue grass" of North America; _P. alpina_ is a
mountain grass of the northern hemisphere and found also in the Arctic
region. The largest species of the genus is _Poa flabellata_ which
forms great tufts 6-7 ft. high with leaves arranged like a fan; it is
a native of the Falkland and certain antarctic islands where it is
known as tussock grass. _Glyceria fluitans_, manna-grass, so-called
from the sweet grain, is one of the best fodder grasses for swampy
meadows; the grain is an article of food in central Europe. _Festuca_
(fescue) is also a large and widely distributed genus, but found
especially in the temperate and cold zones; it includes valuable
pasture grasses, such as _F. ovina_ (sheep's fescue), _F. rubra_; nine
species are British. The closely allied genus _Bromus_ (brome grass)
is also widely distributed but most abundant in the north temperate
zone; _B. erectus_ is a useful forage grass on dry chalky soil.

Tribe 10. _Hordeae_ (about 19 genera, widely distributed; six are
British). _Nardus stricta_ (mat-weed), found on heaths and dry
pastures, is a small perennial with slender rigid stem and leaves, it
is a useless grass, crowding out better sorts. _Lolium perenne_, ray-
(or by corruption rye-) grass, is common in waste places and a
valuable pasture-grass; _L. italicum_ is the Italian ray-grass; _L.
temulentum_ (darnel) contains a narcotic principle in the grain.
_Secale cereale_, rye (q.v.), is cultivated mainly in northern Europe.
_Agropyrum repens_ (couch grass) has a long creeping underground stem,
and is a troublesome weed in cultivated land; the widely creeping stem
of _A. junceum_, found on sandy sea-shores, renders it a useful
sand-binder. _Triticum sativum_ is wheat (q.v.) (fig. 21), and
_Hordeum sativum_, barley (q.v.). _H. murinum_, wild barley, is a
common grass in waste places. _Elymus arenarius_ (lyme grass) occurs
on sandy sea-shores in the north temperate zone and is a useful
sand-binder.

Tribe 11. _Bambuseae_. Contains 23 genera, mainly tropical. See
BAMBOO.