392 



PRACTICAL BOTANY 



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

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

 Avood 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 {Lufiulamhar), 

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



Tig. 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 soniewliat 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 hy R. B. Hough 



In structure the broad-leaved woods may be classed into 

 two groups, — the ring-porous and the lUffvse-porons 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 tlu-oughout the wood of the spring 

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



