Lianas or sometimes herbs, shrubs or trees. Leaves alternate, simple, often cordate or reniform, entire to deeply lobed. Stipules wanting. Flowers solitary or in axillary fascicles or corymbs, actinomorphic or zygomorphic, hermaphrodite. Perianth simple, coloured, united and variously 3-lobed, rarely with 3 rudimentary petals. Stamens 5, 6, 12 or ∞, free or connate to the style. Ovary inferior or half-inferior, mostly 4—6-locular, sometimes nearly apocarpous. Ovary numerous, anatropous, on axile placentas. Fruit a septicidal capsule. Seeds with endosperm and small embryo. About 600 species in 7 genera mostly in the tropics and subtropics, especially in South America; only a few species in the temperate regions.