Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/69

Rh EXAMPLES : Cynodon, CJiloris, Eleusinc, LeptoMoa, Spartina, Ctenium, Nardus. 7. Miliecc. Spikelets one- or several-flowered, paniculate. Flower ing glumes usually rounded and unawned. Palea large. EXAMPLES : Milium, Coslachne, Sporobolus. 8. Fcstucece. Spikelets several- or many-flowered, stalked, panicu late or capitate. Flowering glumes entire, obtuse or acute, or with a straight awn ; one or more empty ones above the fertile flowers. EXAMPLES : Festuca, Brow/us, Lamarkia, Briza, Poa, Era- grostis, Dactylis, Cynosurus, Arundo, Pliragmitcs, Melica. FIG. 11. Poacece. 1. spikelet of Briza ; 2, spikelet of Tri/icum. 9. Bamlusccc. Spikelets one-, several-, or many-flowered, usually sessile, paniculate or capitate. Lodicules three. Stamens generally six. Stems very large and tall (called arbore ous or shrubby). Blade of leaf articulated with the sheath. EXAMPLES : Arundinaria, CJmsquea, Nastus, Bambusa, Mclo- canna, Beeslia. 10. Hordeae. Spikelets one- or several-flowered, sessile on the opposite sides of the main axis of the spike. Otherwise as in Festucece. EXAMPLES : Ifordcum, Agropyrum, dSgilops, Triticum, Lolium, Lcpturus, Elymus. [5 to 10 compose Bentham s tribe AstrcptcK.]

.&mdash;Grasses are the most universally diffused over the globe of all flowering-plants. There is no district in which they do not occur, and in nearly all they are a leading and dominant feature of the flora. In actual number of species Graminece comes considerably after Com posite? and Leguminosce, the two most numerous orders of phanerogams, but in number of individual plants it pro bably far exceeds either; whilst from the wide extension of many of its species, the proportion of Graminece to other orders in the various floras of the world is much higher than its whole number of species would lead one to expect. This number can, however, scarcely be put much below 6000, which is probably somewhat more than a fifth of all monocotyledons. This is only about T^th of the phanero gams as a whole, yet in any given locality, with a very few exceptions, this proportion is largely exceeded. In tropical regions, where Leguminosce is the leading order, grasses closely follow as the second, whilst in the warm and tempsrate regions of the northern hemisphere, in which Composite takes the lead, Graminece again occupies the second position. As the colder latitudes are entered the grasses become relatively more numerous, and are the lead ing family in Arctic and Antarctic regions. The only countries where the order plays a distinctly subor Jinate part are some extra-tropical regions of the southern hemisphere, Australia, the Cape, Chili, &c. The actual proportion of graminaceous species to the whole phanerogamic flora in different countries is found to vary from nearly ^th in the Arctic regions to about ^th at the Cape ; in the British Isles it is about T th. The following are proportions per cent, in various floras, from Decandolle s Geogr. Botanique, which must, however, be taken as merely approximations in most cases&thinsp;:&mdash;

The principal climatic cause influencing the number of graminaceous species appears to be amount of moisture ; it is only in very dry countries that they become distinctly less numerous. A remarkable feature of the distribution of grasses is its uniformity ; there are no great centres for the order, as in Composite?, where a marked preponderance of endemic species exists ; and the genera, except some of the smallest or monotypic ones, have usually a wide distri bution. Speaking generally, however, the Panicacece are tropical and warm temperate plants, whilst the grasses of temperate and colder regions are members of the Poacece. The former are very sparingly represented in Europe by a few species of the vast tropical genera Andropogon and Panicum. Poacece, on the other hand, form a fair pro portion of tropical Graminece, especially in the higher dis tricts where, as in the mountains of Abyssinia, are several endemic genera and many species. The largest tropical genus of Poacece is Eragrostis. The distribution of the tropical tribe Hamliisece is in teresting. There are 170 or more species, which are about equally divided between the Indo-Malayan region and tropical America, only one species being common to both. Apparently there is but a single native species on the African continent, where it has a wide range, and none are recorded for Australia, though species may perhaps occur on the northern coast One species of Ariindinana reaches north wards as far as Virginia, and the elevation attained in the Andes by some species of CJmsquea is very remarkable, one, C. aristata, being abundant from 15,000 feet up to nearly the level of perpetual snow. Many grasses are almost cosmopolitan, such as our common reed, Phragmites communis ; and many range throughout the warm regions of the globe, e.g., Cynodon Dactylon, Eleusine indica, Imperata arimdinacea, Sjiorobolvs indicus, &c., and such weeds of cultivation as species of Setaria, Ec.hinochloa, which are found over both Old and New Worlds. The recent masterly revision of the whole 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 1 4 are endemic, 1 extends to South Africa, 3 are common to Australia and New Zealand, 18 extend also into Asia, whilst no less 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 has only occasionally occurred at intervals in three or four isolated spots in Europe (Norway, Bohemia, Normandy). Many remarkable endemic genera occur in tropical America, including Anomockloa 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 Saliinii, B. Br., of Melville Island.

