Herbs or rarely shrubs. Leaves alternate or opposite, without stipules. Flowers irregular or almost regular, bisexual. Calyx persistent, with 4–5 lobes or teeth. Corolla usually tubular, occasionally rotate, 2-lipped or nearly regular; the limb with 4–5 lobes, imbricate in the bud. Stamens 4 (in pairs, 2 long and 2 short), rarely 5 or 2. Ovary superior, 2-locular; placentas axile; style solitary. Fruit a 2-locular capsule opening by valves or pores. 220–250 gen. cosmop.