286 THE BOOK OF FORESTRY 



3. Pores in summer wood small, distributed singly, in 



groups or in mostly short, broken tangential lines. 

 a. Odorless, tasteless. Lines of pores in summer 

 wood short, narrow, of few open pores, mostly 

 near the margin of the growth ring. Pores 

 in the spring wood in rather broad zone, 

 numerous. Pith rays uniform, narrow, in- 

 conspicuous, almost invisible on cross-section 

 to naked eye. 



WHITE ASH Fraxinus americana 



4. Pores in summer wood isolated or fairly evenly dis- 



tributed; not in groups or lines, comparatively 

 large, often approaching in size those of early 

 wood. Pores in spring wood moderately large, not 

 abundant, usually in very irregular zone. Rays 

 uniform, not conpsicuous, abundant. 

 a. Wood heavy, hard, tough, strong; sapwood white; 

 heartwood brown. 



SHAGBARK Hicoria ovata 



5. Pith rays fine but distinct. 



a. Very heavy and hard. Heartwood yellowish 

 brown. Xyloses present. 



BLACK LOCUST Robinia pseudacaria 



B. Diffuse porous woods. 



1. Growth rings absent or indistinct; when present not 



corresponding to annual periods and not separable 

 into early and late wood. 

 a. Broad rays absent. Pores uniform in size, rather 



large and conspicuous, equally distributed. 



Rays fine but distinct, producing "silver 



grain" on radial surface. Color rich reddish 



brown to light brown. 



MAHOGANY Swietenia mahogoni 



2. Growth rings distinct, corresponding to annual periods. 

 a. Pores varying in size from large to minute, largest 



in spring wood approaching ring porous ar- 

 rangement. 



al. Heavy and hard; heartwood chocolate brown, 

 sapwood nearly white. 



BLACK WALNUT Juglans nigra 



