Annual or perennial herbs, rarely undershrubs. Leaves opposite, simple, entire, generally united at the base by a transverse line. Stipules small, scarious or wanting. Flowers actinomorphic, solitary or in cymose inflorescences, hermaphrodite or rarely unisexual. Sepals 4—5, united or free, persistent. Petals as many as the sepals or wanting. Stamens 8—10 or less, inserted with the petals; anthers 2-celled with longitudinal dehiscence. Ovary superior, uni-locular or rarely basically 2—5-locular; styles 2—5 or one style with 2—5 stigmas; ovules one to numerous, central, campylotropous or anatropous. Fruit a capsule, dehiscing by valves or by apical teeth, rarely baccate. Embryo curved, surrounding the mealy endosperm; the cotyledons narrow. About 1500 species, widely distributed in the temperate regions, rarely in the tropics.