_The Forest Regions._--The great treeless region east of the Rocky Mountains separates the wooded area of the United States into two grand divisions, which may be called the Eastern and the Western forests. The Eastern forest is characterized by the predominance, on the whole, of broad-leafed trees, the comparative uniformity of its general types over wide areas, and its naturally unbroken distribution. In the Western forest conifers are conspicuously predominant; the individual species often reaches enormous and even unequalled dimensions, the forest is frequently interrupted by treeless areas, and the transitions from one type to another are often exceedingly abrupt. Both divisions are botanically and commercially rich in species.
The Eastern forest may conveniently be subdivided into three members:
1. The Northern forest, marked by great density and large volume of standing timber, and a comparative immunity, in its virgin condition, from fire. The characteristic trees are maples, birches and beech (_Fagus atropunicea_), among the hardwoods and white pine (_Pinus strobus_), spruce (_Picea rubens_ and _Picea mariana_) and hemlock (_Tsuga canadensis_) among conifers.
2. The Southern forest is on the whole less dense than the Northern, and more frequently burned over. Among its characteristic trees are the longleaf (_Pinus palustris_) and other pines, oaks, gums, bald cypress (_Taxodium distichum_) and white cedar (_Chamaecyparis thyoides_).
3. The Central Hardwood forest, which differs comparatively little from adjacent portions of the Northern and Southern forests except in the absence of conifers. Among its trees are the chestnut (_Castanea dentata_), hickories, ashes and other hardwoods already mentioned.
1. The Pacific Coast forest, marked by the great size of its trees and the vast accumulations of merchantable timber. Among its characteristic species are the redwood (_Sequoia sempervirens_) and the big tree (_S. Washingtoniana_), the Douglas fir (_Pseudotsuga taxifolia_), sugar pine (_Pinus lambertiana_), western hemlock (_Tsuga heterophylla_), giant arborvitae (_Thuja plicata_) and Sitka spruce (_Picea sitchensis_).
2. The Rocky Mountain forest, whose characteristic species are the western yellow pine (_Pinus ponderosa_), Engelmann spruce (_Picea engelmanni_) and lodgepole pine (_Pinus murrayana_). This forest is frequently broken by treeless areas of greater or less extent, especially towards the south, and it suffers greatly from fire. Subarid in character, except to the north and at high elevations, the vast mining interests of the region and its treeless surroundings give this forest an economic value out of proportion to the quantities of timber it contains.
