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..2 Pistillate scales woody, forming a persistent conelike catkin; plant a shrub, < 4 m tall (except A. glutinosa)
..2 Pistillate scales deciduous with or soon after the fruits; plant a tree, > 10 m tall at maturity
....3 Nut spherical, 1-1.5 cm in diameter, closely enveloped by the involucre
......4 Infructescence bracts flat, 1-3 lobed, not enclosing the nut; bark gray, smooth; trunk moderately to strongly fluted; buds 4-angled
......4 Infructescence bracts inflated, loosely enclosing the nut; bark brown, shreddy; trunk not fluted; buds not 4-angled