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1 Scales of the pistillate catkins persistent; leafy involucre absent; fruit a small winged nut; [subfamily Betuloideae]. | |
2 Pistillate scales woody, forming a persistent conelike catkin; plant a shrub, < 4 m tall (except A. glutinosa) | |
1 Scales of the pistillate catkins caducous; leafy involucre present, conspicuous; fruit an unwinged nut; [subfamily Coryloideae]. | |
4 Infructescence bracts flat, 1-3 lobed, not enclosing the nut; bark gray, smooth; trunk moderately to strongly fluted; buds 4-angled | |