KEY TO THE SPECIES OF BIRCHES 



Leaves with 9-12 pairs of veins; fruit erect, oblong-ovoid; wing 

 not as broad as nutlet; twigs with wintergreen flavor; important 

 eastern timber species. 



2. Bark dark, furrowed, not separating into papery layers; bracts 

 of fruit glabrous B. lenta, Sweet Birch, p. 153. 



2. Bark dirty-yellow, separating into thin papery layers; bracts 

 of fruit hairy B. alleghaniensis, Yellow Birch, p. 151. 



Leaves with 8 or less pairs of veins (7-9 in River Birch); fruit 

 oblong or cylindric; twigs without wintergreen flavor. 



3. Bark red-brown to chestnut-brown. 



4. Bark separating freely into papery layers; fruit erect; wing 



much narrower than nutlet; eastern 



B. nigra, River Birch, p. 151. 



4. Bark not separating into papery layers; fruit pendent; wing 

 broader than nutlet; western. 

 5. Fruit Vi-V'^ inch long; leaves wedge-shaped at base; 



western Canada and Alaska 



fi. X eastwoodiae, Yukon Birch, p. 155. 



5. Fruit 1-1 V4 inches long; leaves usually rounded at base; 



western United States and southwestern Canada 



B. occidentalis , Water Birch, p. 1 55. 



3. Bark distinctly white in color. 



6. Bark chalky-white, not separating freely into papery layers; 

 leaves triangular or rhombic, bright green; Delaware and 



Pennsylvania to eastern Canada 



B. populifolia. Gray Birch, p. 153. 



6. Bark lustrous, pink-white, separating freely into papery 

 layers; leaves usually ovate to oval. 



7. Young twigs hairy and nearly non-glandular; bracts of 

 fruit with middle lobe much longer than lateral lobes; 



Northern transcontinental 



B. papyrifera, Paper Birch, p. 149. 



7. Young twigs glabrous and resinous-glandular; bracts of 

 fruit with middle lobe not longer than lateral lobes. 

 8. Leaves hairy along veins on lower surface; small tree 



from Vermont north to east Canada 



B. caerulea-grandis, Blueleaf Birch, p. 149, 



8. Leaves strictly glabrous; a handsome, widely culti- 

 vated, Eurasian tree; often with pendulous branches 

 and lobed leaves. . B. pendula, European Birch, p. 146. 



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