Annual or perennial herbs or shrubs. Leaves opposite and alternate, usually entire. Flowers often showy, axillary and solitary, or in terminal racemes or panicles. Calyx-tube adnate to the ovary; limb with usually 2 or 4 valvate large lobes.

Petals 2 or 4, rarely more, fugacious, twisted. Stamens 1 to 8. Fruit variable. About twenty genera and 300 species are grouped together under this head. Most of the species are found in temperate regions.