WINTER KEY TO THE SPECIES OF BETULA 



a. Bark of trunk white, separating freely into thin, papery lay- 

 ers; twigs without wintergreen taste. 5. alba papyrif era, $. 91. 



aa. Bark of trunk not white, usually dark colored, not separat- 

 .ing into papery layers; twigs with more or less wintergreen 

 taste. 



b. Bark dirty-yellow, breaking into strips more or less curled 



at the edges; twigs with slight wintergreen taste 



B. lutea, p. 89, 



bb. Bark dark red-brown, cleaving off in thick, irregular plates 

 (resembles bark of Black Cherry) ; twigs with strong 

 wintergreen taste B. lenta, p. 87. 



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