Trees, monoecious, deciduous. Leaves alternate; stipules not seen; petiole usually with a single or pair of small, rounded glands at apex on adaxial surface, sometimes with additional glands along distal half of petiole; leaf blade palmately 3-5-veined at base, margin glandular-serrate. Flowers hypogynous, unisexual, in terminal or rarely axillary many flowered panicles, pistillate flowers in upper part of inflorescence, staminate ones in lower part; bracts present; pedicels articulate. Sepals 5, valvate, nearly free, texture rather thick. Petals absent. Disk glands absent. Staminate flowers: stamens many, free, shorter than sepals; anthers ellipsoid or transverse-ellipsoid, connective much dilated, curved, bringing both locules to face in same direction (toward periphery of flower); abortive ovary very small. Pistillate flowers: staminodes many, surrounding ovary base, resembling small stamens; ovary superior, 1-loculed; placentas 3 or 4, filiform, finally woody, persistent; ovules numerous; styles 3, narrowly cylindric, joined in basal 1/3, with free distal parts strongly reflexed against ovary; stigmas flattened, triangular, lobed. Capsule narrowly ovoid, 3-valvate; outer layer of pericarp thin, dehiscent; inner layer thin, woody, persistent; valves characteristically splitting from apex and base and remaining attached by persistent woody placental strips; styles caducous. Seeds many, arranged vertically, compressed-flat, winged; wing flat, papery, completely encircling seed, seed proper less than 1/2 as long as wing.

● One species: China.