SUMMER KEY TO THE SPECIES OF BETULA

a.Bark of trunk white, separating freely into thin, paperylayers; twigs without wintergreen taste; leaves usually solitary,not aromatic.B. alba papyrifera, p. [91].
aa.Bark of trunk not white, usually dark colored, not separatingfreely into papery layers; twigs with more or less wintergreentaste; leaves solitary or in pairs, aromatic.
b.Bark dirty-yellow, breaking into strips more or less curledat the edges; leaves solitary or in pairs, slightly aromatic;twigs with slight wintergreen tasteB. lutea, p. [89].
bb.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].

WINTER KEY TO THE SPECIES OF BETULA

a.Bark of trunk white, separating freely into thin, papery layers;twigs without wintergreen taste.B. alba papyrifera, p. [91].
aa.Bark of trunk not white, usually dark colored, not separatinginto papery layers; twigs with more or less wintergreentaste.
b.Bark dirty-yellow, breaking into strips more or less curledat 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 strongwintergreen taste.B. lenta, p. [87].