392 



PRACTICAL BOTANY 



tool handles, and for carriage spokes; beech for shoemakers' 

 lasts, saw handles, and carpenters' planes; persimmon for 

 wood turning and shoe lasts ; black locust for posts and rail- 

 road ties (on account of its durability in the ground). 



For cabinetwork the most valued of our hard woods are 

 black walnut, cherry, birch, and a good many species of oak 

 and of ash. White walnut, red or sweet gum (Liquidambar), 

 sycamore, and holly are also used, although not so largely. 



FIG. 318. Cross section of diffuse-porous woods 



A, coarse-grained wood of sycamore ; B, fine-grained wood of holly. The wood is 

 diffuse-porous because the ducts are formed somewhat equally throughout the 

 season's growth ; the dark streaks running nearly vertically on the page, as the 

 sections are here placed, are medullary rays (shown more clearly in Fig. 35). Mag- 

 nified fifteen diameters. Photomicrograph by R. B. Hough 



In structure the broad-leaved woods may be classed into 

 two groups, the ring-porous and the diffuse-porous kinds. In 

 the former group (Fig. 317) most of the conspicuous ducts 

 (the cut-off ends of which appear as pores in the cross section) 

 are found in the spring wood. In the latter the ducts are scat- 

 tered somewhat generally throughout the wood of the spring 

 and summer growth (Fig. 318). Among the commonest and 



