10 WOOD AND FOREST. 



the dimensions of trees. They are strikingly distinguished by the 

 structure of their stems. They have no cambium layer and no dis- 

 tinct 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 struc- 

 ture is not in annual rings, but irregular. These one seed-leaf tree? 

 (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. f cocoanut-palm and porcupine wood are so used. 



The most useful of the monocotyledons, or endogens, ("inside 

 growers," as they are sometimes called,) are the bamboos, which are 

 giant members of the group of grasses, Fig. 1. They grow in dense 

 forests, some varieties often 70 feet high and 6 inches in diameter, 

 shooting up their entire height in a single season. Bamboo is very 

 highly valued in the Orient, where it is used for masts, for house 

 rafters, and other building purposes, for gutters and water-pipes 

 and in countless other ways. It is twice as strong as any of our 

 woods. 



Under the fruit-bearing trees (angiosperms), timber trees arc 

 chiefly found among those that have two seed-leaves (the dicotyle- 

 dons) and include the great mass of broad-leaved or deciduous trees, 

 such as chestnut, oak, ,ash and maple. It is to these and to the coni- 

 fers that our principal attention will be given, since they constitute 

 the bulk of the wood in common use. 



The timber-bearing trees, then, are the : 



(1) Conifers, the needle-leaved, naked-seeded trees, such as pine, 

 cedar, etc. Fig. 45, p. 199. 



(2) Endogens, which have one seed-leaf, such as bamboos, Fig. 1^ 



(3) Broad-leaved trees, having two seed-leaves, such as oak, 

 beech, and elm. Fig. 48, p. 202. 



The common classifications of trees are quite inaccurate. Many 

 of the so-called deciduous (Latin, deciduus, falling off) trees are 

 evergreen, such as holly, and, in the south, live oak, magnolia and 

 cherry. So, too, some of the alleged "evergreens," like bald cypress 

 and tamarack, shed their leaves annually. 



