10-1 l^'lEI.D ManIJAI. 



hard and strong, [n dr}' or moist soil. Cape Breton I. to 

 Man., Fla., Neb., Kan., and Tex.. 



59. Betula (Tourn.) L. Birch. 



Trees or shrubs with simple, serrate, 2-ranked leaves ; 

 v/ith small samara-like nuts in a cone-like ament, and fre- 

 quently with paper}^ or leathery bark. 



Usually aromatic, monecious, styles 2, ovulary bilocular. 



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

 serrate, only slightly doubly serrate; bark brown or 

 yellowish, close or separating into layers; bark of 

 twigs with wintergreen flavor; fruiting aments sessile 

 or nearly so. 2. 



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



cordate, prominently 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. 3. 



2. Bark not separating in laj^ers, becoming furrowed ; leaves 



shining above ; fruiting bracts glabrous or pubescent, 

 less than i in. long, lobed at the apex. B. lenta. 



2. Bark separating in papery layers when old, somewhat 



silvery; leaves dull above; fruiting bracts ciliate, 

 more than y in. long, lobed to about the middle. B 

 lutea. 



3. Bark greenish or reddish brown, peeling in papery layers 



especially above; leaves rhombic, acute at both ends; 

 young leaves, twigs, and aments tomentose ; fruiting 

 aments oblong, erect. B. nigra. 



3. Bark of trunk and larger branches chalky white, usually 



peeling off in thin layers; fruiting aments cylindrical, 

 pendant or spreading. 4. 



4. Leaves deltoid, very long acuminate at the apex; bark 



not readily separable into thin layers ; twigs with 

 numerous resinous glands. B. populifolia. 



4. Leaves acute or acuminate, usually ovate, in some culti- 



vated forms of various shapes; bark peeling off in 

 thin layers, o. 



5. Leaves ovate or suboricular; native, occasionally culti- 



vated. B. papyrifera. 



