Annual or perennial herbs of erect or rarely climbing habit, rarely shrubs. Leaves opposite or alternate, simple or compound. Inflorescence various. Flowers regular, pentamerous. Calyx inferior, 5-lobed. Corolla slightly perigynous, campanulate, funnel-shaped or salver-shaped. Stamens 5, inserted upon the corolla-tube and alternating with its lobes. Fruit a 3-celled 3-valved few or many-seeded capsule, splitting loculicidally. Seeds angular, winged or oval, with spongy testa and fleshy or horny albumen. A small order confined to temperate and cold regions, especially numerous in North-western America. There are 17 genera and upwards of 100 species.