are included in the descriptions as an assistance in identification. The natural range of the forest trees, and the regions where they abound in commercial quantities, are outlined according to the latest and best authorities. Estimates of present and future supply are offered, where such exist that seem to be authoritative. The trees are given the common and the botanical names recognized as official by the United States Forest Service. This lessens misunderstanding and confusion in the discussion of species whose common names are not the same in different regions, and whose botanical names are not agreed upon among scientific men who mention or describe them. The forests of the United States contain more than five hundred kinds of trees, ranging in size from the California sequoias, which attain diameters of twenty feet or more and heights exceeding two hundred, down to indefinite but very small dimensions. The separating line between trees and shrubs is not determined by size alone. In a general way, shrubs may be considered smaller than trees, but a seedling tree, no matter how small, is not properly called a shrub. It is customary, not only among botanists, but also among persons who do not usually recognize exact scientific terms and distinctions, to apply the name tree to all woody plants which produce naturally in their native habitat one main, erect stem, bearing a definite crown, no matter what size they may attain. The commercial timbers of this country are divided into two classes, hardwoods and softwoods. The division is for convenience, and is sanctioned by custom, but it is not based on the actual hardness and softness of the different woods. The division has, however, a scientific basis founded on the mechanical structures of the two classes of woods, and there is little disagreement among either those who use forest products or manufacture them, or those who investigate the actual structure of the woods themselves, as to which belong in the hardwood and which in the softwood class.