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 papyri f era, 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. luted, p. 89. 



t>b. Bark dark red-brown, cleaving 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 



