Hagenia J.F.Gmel.

Dioecious or polygamous tree. Leaves imparipinnate. Flowers small, anemophilous, aggregated into large many-flowered panicles. Petals 0 or rudimentary. Calyx adnate to the receptacle, apically produced into (4–)5 lobes (“bracteoles”). Receptacle closed at the throat, terminating in (4–)5 (inner) lobes which usually alternate with the calyx-lobes: thus each flower bears an “inner” and an “outer” row of calyx-lobes, all membranous. Male flowers with the outer calyx-lobes smaller than the inner, the receptacle not accrescent, the ovaries aborting; stamens 12–20. Female flowers with the outer calyx-lobes and receptacle accrescent, the outer lobes much larger than the inner and serving ultimately to parachute the ripe fruit by rotation; stamens with very short filaments and abortive anthers; styles 2; carpels 2, free within the receptacle; ovule single, pendant. Hermaphrodite flowers apparently rare, similar to ♀ flowers but having (at least some) fertile anthers. Achenes brown, (often only 1 developing), reticulately rugose, ± ovoid with a thin, fragile pericarp.