Annual or perennial herbs. Leaves, at least below, opposite and entire, sometimes alternate above. Inflorescences of cymes, panicles or thyrses. Calyx narrow, toothed or lobed, eventually ruptured by the maturing fruit. Corolla showy, salver-shaped; tube narrow and constricted at the throat; lobes obovate to circular. Stamens attached at different heights on the corolla tube. Style usually filiform. Capsule 3-valved, septicidal.