Fls. us. functionally unisexual, irregular, in cymose racemes or panicles; sepals us. 5, petals 5 or 0; disk extrastaminal, glandular. Stamens hypog., us. 8 or 10; filaments often hairy. Ovary superior, us. 3-loculed; ovules 1-2 per locule, on axile placentae; stigma us. 1, lobed; seeds often arillate; fr. various. Mostly polygamodioec. trees, shrubs or lianes with alt., compound or simple, exstipulate lvs. About 130 genera and 1100 spp., largely tropical.

Monoecious or more rarely dioecious, usually deciduous trees or shrubs. Lvs opposite, exstipulate, simple, usually palmately toothed or lobed, less commonly pinnately compound with up to 15 leaflets. Fls actinomorphic, small, hypogynous or perigynous, arranged in fascicles, corymbs, racemes or panicles. Sepals 4-5. Petals usually 4-5, sometimes 0. Stamens (4)-8-(10), inserted on or inside the usually well-developed disc. Ovary superior, 2-celled, compressed, with septum along the short axis; ovules 2 in each cell; styles 2, free or united below. Fr. schizocarpic, splitting into 2 samaras; wing on upper side or occasionally extending round the seed. Seed non-endospermic; cotyledons flat or plicate, often green.

Trees or large shrubs, usually andromonoecious. Lvs opposite, digitately compound, exstipulate. Fls in large terminal racemes or panicles, zygomorphic. Sepals (4)-5, mostly connate and forming a tube. Petals (4)-5, free, unequal, imbricate, clawed. Stamens 5-9, free, inserted within an entire annular or excentric disc. Ovary superior, (1)-3-celled; ovules 2 per cell; style elongated and stigma simple. Fr. a large coriaceous capsule, smooth or echinate, usually 1-celled, opening by 3 valves. Seed usually 1, large, non-endospermic; cotyledons thick and often adherent adaxially; hilum large.