134 Proceedings of the Ohio State Academy of Science 



17. Ostrya Scop. Hop-hornbeam. 



Monoecious trees with the flowers in aments. Leaves with 

 straight and parallel lateral veins. Nuts small, in a hop-like 

 catkin. 



I. Ostrya virginiana (Mill.) AVilld. Hop-hornbeam. 

 A small tree with scaly bark. Wood white, compact, and very 

 strong. In dry or moist soil. Cape Breton I. to Minn., Fla., 

 Neb., Kan., Tex., and Ohio. 



18. Betula L. Birch. 



Aromatic, monoecious trees or shrubs ; bark usually papery 

 or leathery ; nuts small, samara-like, in a cone-like ament. 



1 . Leaves acute, obtuse, or truncate at the base, rarely cordate, prom- 

 inently doubly serrate or serrate-dentate : bark chalky white or 

 greenish brown ; bark of twigs not with the flavor of wintergreen, 

 usually bitter ; fruiting aments peduncled. 2. 



1. Leaves usually cordate or rounded at the base, sharply serrate, only 



slightly doubly serrate ; bark brown or yellowish, close or separat- 

 ing into layers ; bark of twigs with wintergreen flavor ; fruiting 

 aments sessile or nearly so. 5. 



2. Bark of trunk and larger branches chalky white, usually peeling off 



in thin layers ; fruiting aments cylindrical, pendant or spreading. 3. 



2. Bark greenish brown, hardly peeling in layers; leaves rhombic, 



acute at both ends ; young leaves and twigs tomentose ; fruiting 

 aments oblong, erect. B. nigra. 



3. Leaves deltoid, very long acuminate at the apex; bark not readily 



separable into thin layers ; twigs with numerous resinous glands. 

 B. populifolia. 



3. Leaves acute or acuminate, usually ovate, in some cultivated forms 



of various shapes ; bark peeling off in thin layers. 4. 



4. Leaves various, commonly triangular or rhombic-ovate, on slender 



petioles ; twigs pendulous or weeping ; much cultivated, from 

 Europe and Asia. B. alba. 



4. Leaves ovate or suborbicular ; twigs pendulous; native, occasionally 



cultivated. B. papyrifera. 



5. Bark not separating in layers, becoming furrowed; leaves shining 



above ; fruiting bracts less than J in. long, lobed at the apex. 

 B. lent a. 

 5. Bark separating in layers or sometimes close, somewhat silvery; 

 leaves dull above ; fruiting bracts more than \ in. long, lobed to 

 about the middle. B. lutea. 



