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—Frazinus 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. Tyloses present. 
BLACK LOCUST—Robinia pseudacacia 
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 
erain’’ on radial surface. Color rich reddish 
brown to light brown. 
MAIIOGAN s—Swretenia mahogonr 
2. Growth rings distinct, corresponding to annual periods. 
a. Pores varying 1n 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 
