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......... 
ene ne ere renee B. lutea, p. 80. 
bb. Bark dark red-brown, cleaving off in thick, irregular plates 
(resembles bark of Black Cherry); twigs with strong 
wintergreen taste. ........ cee cee eee eee eee B. lenta, p. 87. 
