134 Proceedings of the Ohio State Academy of Science 



17. Ostrya Scoj). Hop-hornbeam. 



Monoecious trees willi the flowers in aments. Leaves with 

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

 catkin. 



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

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

 strong. In dry or moist soil. Cape Breton I. to ^linn., 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, oljtuse, 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 ofif 



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 ofif 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 \ in. long, lobed at the apex. 

 B. lenta. 

 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. lutca. 



