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.

III. DISTRIBUTION.--Grasses are the most universally diffused of all flowering plants. There is no district in which they do not occur, and in nearly all they are a leading feature of the flora. In number of species Gramineae comes considerably after Compositae and Leguminosae, the two most numerous orders of phanerogams, but in number of individual plants it probably far exceeds either; whilst from the wide extension of many of its species, the proportion of Gramineae to other orders in the various floras of the world is much higher than its number of species would lead one to expect. In tropical regions, where Leguminosae is the leading order, grasses closely follow as the second, whilst in the warm and temperate regions of the northern hemisphere, in which Compositae takes the lead, Gramineae again occupies the second position.

While the greatest number of species is found in the tropical zone, the number of individuals is greater in the temperate zones, where they form extended areas of turf. Turf- or meadow-formation depends upon uniform rainfall. Grasses also characterize steppes and savannas, where they form scattered tufts. The bamboos are a feature of tropical forest vegetation, especially in the monsoon region. As the colder latitudes are entered the grasses become relatively more numerous, and are the leading family in Arctic and Antarctic regions. The only countries where the order plays a distinctly subordinate part are some extra-tropical regions of the southern hemisphere, Australia, the Cape, Chili, &c. The proportion of graminaceous species to the whole phanerogamic flora in different countries is found to vary from nearly 1/4th in the Arctic regions to about 1/25th at the Cape; in the British Isles it is about 1/12th.

The principal climatic cause influencing the number of graminaceous species appears to be amount of moisture. A remarkable feature of the distribution of grasses is its uniformity; there are no great centres for the order, as in Compositae, where a marked preponderance of endemic species exists; and the genera, except some of the smallest or monotypic ones, have usually a wide distribution.

The distribution of the tropical tribe _Bambuseae_ is interesting. The species are about equally divided between the Indo-Malayan region and tropical America, only one species being common to both. The tribe is very poorly represented in tropical Africa; one species _Oxytenanthera abyssinica_ has a wide range, and three monotypic genera are endemic in western tropical Africa. None is recorded for Australia, though species may perhaps occur on the northern coast. One species of _Arundinaria_ reaches northwards as far as Virginia, and the elevation attained in the Andes by some species of _Chusquea_ is very remarkable,--one, _C. aristata_, being abundant from 15,000 ft. up to nearly the level of perpetual snow.

Many grasses are almost cosmopolitan, such as the common reed, _Phragmites communis_; and many range throughout the warm regions of the globe, e.g. _Cynodon Dactylon_, _Eleusine indica_, _Imperata arundinacea_, _Sporobolus indicus_, &c., and such weeds of cultivation as species of _Setaria_, _Echinochloa_. Several species of the north temperate zone, such as _Poa nemoralis_, _P. pratensis_, _Festuca ovina_, _F. rubra_ and others, are absent in the tropics but reappear in the antarctic regions; others (e.g. _Phleum alpinum_) appear in isolated positions on high mountains in the intervening tropics. No tribe is confined to one hemisphere and no large genus to any one floral region; facts which indicate that the separation of the tribes goes back to very ancient times. The revision of the Australian species by Bentham well exhibits the wide range of the genera of the order in a flora generally so peculiar and restricted as that of Australia. Thus of the 90 indigenous genera (many monotypic or very small) only 14 are endemic, 1 extends to South Africa, 3 are common to Australia and New Zealand, 18 extend also into Asia, whilst no fewer than 54 are found in both the Old and New Worlds; 26 being chiefly tropical and 28 chiefly extra-tropical.

Of specially remarkable species _Lygeum_ is found on the sea-sand of the eastern half of the Mediterranean basin, and the minute _Coleanthus_ occurs in three or four isolated spots in Europe (Norway, Bohemia, Austria, Normandy), in North-east Asia (Amur) and on the Pacific coast of North America (Oregon, Washington). Many remarkable endemic genera occur in tropical America, including _Anomochloa_ of Brazil, and most of the large aquatic species with separated sexes are found in this region. The only genus of flowering plants peculiar to the arctic regions is the beautiful and rare grass _Pleuropogon Sabinii_, of Melville Island.

_Fossil Grasses._--While numerous remains of grass-like leaves are a proof that grasses were widespread and abundantly developed in past geological ages, especially in the Tertiary period, the fossil remains are in most cases too fragmentary and badly preserved for the determination of genera, and conclusions based thereon in explanation of existing geographical distribution are most unsatisfactory. There is, however, justification for referring some specimens to _Arundo_, _Phragmites_, and to the _Bambuseae_.

BIBLIOGRAPHY.--E. Hackel, _The True Grasses_ (translated from Engler and Prantl, _Die naturlichen Pflanzenfamilien_, by F. Lamson Scribner and E. A. Southworth); and _Andropogoneae_ in de Candolle's _Monographiae phanerogamarum_ (Paris, 1889); K. S. Kunth, _Revision des graminees_ (Paris, 1829-1835) and _Agrostographia_ (Stuttgart, 1833); J. C. Doll in Martius and Eichler, _Flora Brasiliensis_, ii. Pts. II. and III. (Munich, 1871-1883); A. W. Eichler, _Bluthendiagramme_ i. 119 (Leipzig, 1875); Bentham and Hooker, _Genera plantarum_, iii. 1074 (London, 1883); H. Baillon, _Histoire des plantes_, xii. 136 (Paris, 1893); J. S. Gamble, "_Bambuseae_ of British India" in _Annals Royal Botanic Gardens, Calcutta_, vii. (1896); John Percival, _Agricultural Botany_ (chapters on "Grasses," 2nd ed., London, 1902). See also accounts of the family in the various great floras, such as Ascherson and Graebner, _Synopsis der mitteleuropaischen Flora_; N. L. Britton and A. Brown, _Illustrated Flora of the Northern United States and Canada_ (New York, 1896); Hooker's _Flora of British India_; _Flora Capensis_ (edited by W. Thiselton-Dyer); Boissier, _Flora orientalis_, &c. &c.

FOOTNOTE:

[1] The word "grass" (O. Eng. _gaers_, _graes_) is common to Teutonic languages, cf. Dutch Ger. Goth, _gras_, Dan. _graes_; the root is the O. Teut. _gra_-, _gro_-, to increase, whence "grow," and "green," the typical colour of growing vegetation. The Indo-European root is seen in Lat. _gramen_. The O. Eng. _grasian_, formed from _graes_, gives "to graze," of cattle feeding on growing herbage, also "grazier," one who grazes or feeds cattle for the market; "to graze," to abrade, to touch lightly in passing, may be a development of this from the idea of close cropping; if it is to be distinguished a possible connexion may be found with "glace" (Fr. _glacer_, glide, slip, Lat. _glacies_, ice), to glance off, the change in form being influenced by "grate," to scrape, scratch (Fr. _gratter_, Ger. _kratzen_).