C. álba.
1. Cárya álba, Nutt. (Shellbark or Shagbark Hickory.) Leaflets 5, the lower pair much smaller, all oblong-lanceolate, taper-pointed, finely serrate, downy beneath when young. Fruit globular, depressed at the top, splitting readily into 4 wholly separate valves. Nut white, sweet, compressed, 4-angled. Husk quite thin for the Hickories. Tree 70 to 90 ft. high, with very shaggy bark, even on quite small trees. Wild throughout, and cultivated.
C. sulcàta.
2. Cárya sulcàta, Nutt. (Big Shellbark. Kingnut.) Leaflets 7 to 9, obovate-acuminate, sharply serrate, the odd one attenuate at base and nearly sessile; downy beneath (more so than Carya alba). Fruit large, oval, 4-ribbed above the middle, with 4 intervening depressions. Husk very thick, entirely separating into 4 valves. Nut large, 1¼ to 2 in. long, dull-whitish, thick-shelled, usually strongly pointed at both ends. Kernel sweet and good. Tree 60 to 90 ft. high, with a shaggy bark of loose, narrow strips on large trees. Quite common west of the Alleghanies.
C. tomentòsa.
3. Cárya tomentòsa, Nutt. (Mockernut. White-heart Hickory.) Leaflets 7 to 9 (mostly 7), lance-obovate, pointed, obscurely serrate or almost entire, the lower surface as well as the twigs and the catkins tomentose when young. Fruit globular or ovoid, usually with a very hard, thick husk slightly united at base. Nut somewhat hexagonal, with a very thick shell and well-flavored kernel. A tall, slender tree, 60 to 100 ft. high, with a rough deeply furrowed, but not shaggy bark. Common on dry hillsides throughout.
C. microcárpa.