Herbs, sometimes saprophytic. Leaves opposite, simple, often connate at the base. Flowers actinomorphic, bisexual, bracteate and bracteolate, arranged in cymose inflorescences or flowers solitary and terminal. Calyx 4—5-merous, tubular, often with discoid scales at the inner base. Corolla 4—5-merous, tubular, salvershaped, the lobes contorted in bud. Stamens implanted in the corolla-tube, as many as the corolla-lobes, episepalous, anthers with distinct filaments or subsessile, 2-celled, introrse, longitudinally dehiscing. Ovary superior, unilocular, with 2 intruded parietal placentas, ovules oo, anatropous. Style simple, stigma 2-lobed to capitate. Fruit a longitudinally dehiscing capsule, seeds oo, small, with a small embryo, endosperm fleshy. About 800 species in 70 genera, all over the world.