SUMMER KEY TO THE SPECIES OF BETULA 



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

 layers; twigs without wintergreen taste; leaves usually soli- 

 tary, not aromatic B. alba papyrifera, p. 91. 



aa. Bark of trunk not white, usually dark colored, not separating 

 freely into papery layers; twigs with more or less winter- 

 green taste ; leaves solitary or in pairs, aromatic, 

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

 at the edges ; leaves solitary or in pairs, slightly aromatic ; 



twigs with slight wintergreen taste B. lutea, p. 89. 



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

 (resembles bark of Black Cherry); -leaves in pairs, 

 strongly aromatic; twigs with strong wintergreen taste.. 

 B. lenta, p. 87. 



84 



