WINTER KEY TO THE SPECIES OF BETULA 



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

 ers; twigs without wintergreen taste. B. alba papyrifera, p. 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. 



85 



