GRASSES IN THE UNITED STATES. The term °grass° is popularly applied to the green herbage on which cattle and other beasts feed, and thus includes many plants which are not botanically related to the true grasses, such as the clovers, alfalfa, sanfoin, vetches, spurry, etc., frequently referred to as aartificial grasses,* while it excludes some of the most important of the true grasses, namely, the cereals. The true grasses constitute the botanical family Gram anew. They are distinguished from related groups of plants in that the leaves are arranged in two opposite rows on the stem, with a single leaf at each joint. The stems (c-ulms) are usually hollow except at the joints, and the base of the leaf forms a sheath which surrounds the stem above the joints. The sheath is us ually extended a short distance above the base of the blade of the leaf, in a delicate, whitish structure closely surrounding the stem, called the ligule, the office of which seems to be to prevent rain-water from percolating between the sheath and the stem. The grass flower usually consists of the following parts: flower ing glume, palet, lodicule, one to six stamens (usually three), and a one-celled ovary usually with two styles tipped with plumose stigmas. The flowers are usually arranged in two rows on opposite sides of the rachilla, constituting a spikelet. At the base of the spikelet are usually two empty glumes. The empty glumes, flowering glumes, and palet constitute the °chaffs° The spikelet may contain one to many flowers. The lodicule, which stands in front of the flowering glume, is very small, usually not noticeable except on close examination. At flowering time, the lodicule becomes greatly swollen, and by this means spreads the flower open. In spikelets that contain several flowers, the palet, or inner chaff, rests with its back against the rachilla, and is concave on the back, with a nerve or keel on either side. The edges of the nalet are overlapped by the edges of the flowering glume, or outer chaff. The spikelets are arranged either in spikes, as in wheat, or in panicles, as in oats. Popularly, these are referred to as the °seed-head,* and this term will be frequently used in this sense in this article. The fruit of the grasses is a seed-like grain, either adherent to the chaff, as in barley, or free from it, as in wheat.
This is one of the largest and most widely disseminated families of plants, and by far the most important to mankind. It includes the cereals, wheat, oats, barley, rye, rice, millet and corn, sugarcane, sorghum, the cane of the Southern canebrakes and the bamboo of the Old World, in addition to the common grasses of the fields and prairies. It furnishes the prin cipal food of both man and beast, and some of the most beautiful ornamental plants (reed, Ravenna grass, plume-grass, ribbon-grass, etc.).
The grasses are the foundations of agriculture. Their principal development is in the temperate zones, though grasses are found wherever veg etation flourishes. Singularly enough, the most important grasses, the cereal grains, are not known in the wild state, and their cultivation extends so far back into antiquity that even their places of origin are unknown. Either their wild counterparts have become extinct or the cereals have been so changed by cultivation that their wild forms are no longer recogniz able. (Wild plants have recently been dis covered in Palestine that are believed to be the progenitors of wheat). There are in all about 4,000 distinct species of grasses known. The species of only two natural orders of flowering plants exceed this number, namely, the Coat positcr and the Leguminosa, though in the num ber of individual plants the grasses far surpass all others. The total number of grass species growing in the United States is about 1,400;• in the limits of the State of Washington about 275 species are found. Originally, nearly half the area of this country consisted of prairies, the principal herbage of which was grasses. The existence of these vast stretches of grass land has never been fully accounted for. It is not due simply to climatic and soil conditions, for many species of trees readily grow on the prairies when placed there by man. In recent years, vast areas that were formerly occupied by grasses have been invaded by various shrubs and trees, particularly the mesquite tree of the Southwest. This has occurred simultaneously with the destruction of the grasses by stock, in dicating that the presence of the grasses is in imical to forest growth. It is well known that grasses thrive best on the more compact soils. On such soils, the abundant growth of grass, with the fires that have swept over these regions in dry seasons from time immemorial, has kept in check those classes of vegetation which could not quickly recuperate after the destruction by fire of their aerial portions. On the coarser types of soil, the sparse growth of grass, and the consequent lack of fuel to feed the fires, has enabled forest trees to become established. These facts, while they do not entirely account for the existence of prairies, are undoubtedly an important element. The prairies are partic ularly developed in the arid and semi-arid regions where frequent drouth has augmented the destruction occasioned by fires, and partic ularly on the heavier soils of that region which retain sufficient moisture to enable the grasses to form a complete covering over the soil.