(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.
 |
| Fig. 19.—Phalarideae. Spikelet of Hierochloe. |
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.
 |
| Fig. 20.—Poa annua. Plant in Flower; about 12 nat. size. 1, one spikelet. |
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.
 |
| Fig. 21.—Spike of Wheat (Triticum sativum). About 23 nat. size. |
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
