CLIMATIC CONDITIONS ; RAINFALL.
The wide range of soil, topography and climate give the United States a rich and varied flora. Tropic species are found in Florida, California, Texas, New Mexico and Arizona, along the southern frontier, while along the Canadian border boreal species abound. In the greater part of the country, as might easily be inferred from its geographi cal situation, the species are those of the north temperate zone and to a large extent are peculiar to North America. (See AMERICA FLORA). The whole number of indigenous species, exclusive of the lower cryptograms, probably amounts to 5,000, and of these many have a very wide range. The number of woody species is about 850, and about half of these are of a size to be called trees. Of the larger and more important, excluding all the smaller ones, and also the tropical species of the southern border States, there are about 150 species which are of economic importance. About 50 of these belong to the Conifers. This coniferous growth extends in enormous volume down the cool, wet Pacific slope to central California; the giant redwoods and sugar-pines, etc., and the huge sequoia, the largest and oldest plants on the earth, being fa mous everywhere. The conifers abound also through Michigan, Wisconsin and Minnesota to southern Missouri and northwestern Arkan sas and to northeastern Texas and Oklahoma. The hickories, sequoias, magnolias, sassafras, etc., so abundant in America are only found in fossil form in the Old World. Many valuable varieties of grasses have originated from native species. Near the Atlantic Goast and along the southern borders European explorers found maize, squashes, tobacco and other use ful plants in cultivation among the aborigines. Central United States has prominent deciduous (hardwood) trees, such as the oak of many varieties, the beech, maple, elm, chestnut, black walnut, hickory, ironwood, pepperage, red mul berry, etc. In the Southern States the yellow
pine holds foremost place. The characteristic forms in the South are the magnolia, palmetto, tulip-tree, plant-tree, pecan, etc., with the cypress everywhere in the swampy regions. The plains are treeless, except a narrow belt along the water courses, and are covered with grasses, grading in the more arid regions into artemesias and cacti. The Cordilleran woods are chiefly conifers on the mountains; on the plains and in the valleys are the yuccas, cactus, etc., as stated above, and whose dense thorny growth is termed chaparral. In the Appala chian Mountains and the upper Mississippi Valley, broad-leaved, deciduous trees, oaks, chestnuts, walnuts, poplars and cherry pre dominate; and in the Great Lake region pines, firs, spruces and larches are most abundant. The timber trees are considered elsewhere under their own heads, oak, ash, etc. (gq.v.), also under LUMBER INDUSTRY OF THE UNITED STATES ; FORESTRY. Other economic products of the native flora fall naturally into the'classes of fruits, nuts and forage grasses. The native nuts include pecans, walnuts, chestnuts and pine nuts. The fruits include wild raspberries, blackberries, blueberries, elderberries, cran berries and serviceberry. The principal varieties of grasses are Kentucky blue grass, grama grass, bunch grass, buffalo grass, the clovers, lupine and white sage. To these must be added the hundreds of plants of all sorts from fungi to trees which have been introduced since the white settlement. Some are of economic value while others are among our most noxious and troublesome weeds. The white daisy is one of the latter as also the buttercu, dandelion, chickory and thistle. Chinese, Japanese and Mexican species have been introduced with success in California. The eucalyptus, several species of palms, English walnut, olive, prune, almond, etc., are now grown successfully.