When it is remembered that the suitability of wood for a particular purpose depends most of all upon its internal structure, it is plain that the woodworker should know the essential characteristics of that structure. While his main interest in wood is as lumber, dead material to be used in woodworking, he can properly understand its structure only by knowing something of it as a live, growing organism. To facilitate this, a knowledge of its position in the plant world is helpful. All the useful woods are to be found in the highest sub-kingdom of the plant world, the flowering plants or Phanerogamia of the botanist. These flowering plants are to be classified as follows: { I. Gymnosperms. (Naked seeds.) { 1. Cycadaceae. (Palms, ferns, etc.) { 2. Gnetaceae. (Joint firs.) { 3. Conifers. Pines, firs, etc. Phanerogamia, { II. Angiosperms. (Fruits.) (Flowering plants) { 1. Monocotyledons. (One seed-leaf.) { (Palms, bamboos, grasses, etc.) { 2. Dicotyledons. (Two seed-leaves.) { a. Herbs. { b. Broad-leaved trees. Under the division of naked-seeded plants (gymnosperms), practically the only valuable timber-bearing plants are the needle-leaved trees or the conifers, including such trees as the pines, cedars, spruces, firs, etc. Their wood grows rapidly in concentric annual rings, like that of the broad-leaved trees; is easily worked, and is more widely used than the wood of any other class of trees. Of fruit-bearing trees (angiosperms), there are two classes, those that have one seed-leaf as they germinate, and those that have two seed-leaves. The one seed-leaf plants (monocotyledons) include the grasses, lilies, bananas, palms, etc. Of these there are only a few that reach the dimensions of trees. They are strikingly distinguished by the structure of their stems. They have no cambium layer and no distinct bark and pith; they have unbranched stems, which as a rule do not increase in diameter after the first stages of growth, but grow only terminally. Instead of having concentric annual rings and thus growing larger year by year, the woody tissue grows here and there thru the stem, but mostly crowded together toward the outer surfaces. Even where there is radial growth, as in yucca, the structure is not in annual rings, but irregular. These one seed-leaf trees (monocotyledons) are not of much economic value as lumber, being used chiefly "in the round," and to some extent for veneers and inlays; _e.g._, cocoanut-palm and porcupine wood are so used.