Annual or perennial herbs, sometimes woody towards base. Lvs mostly opposite, entire. Fls usually in corymbose or paniculate cymes, sometimes solitary, often showy, pedicellate. Calyx tubular to narrow-campanulate, prominently lobed, often with a scarious membrane below the sinuses, developing with fr. but ruptured at maturity. Corolla strongly convolute, salverform; tube slender, constricted at throat; lobes broad, often emarginate to lobed. Stamens inserted at different levels, included. Style included; stigmas 3; ovules 1-few in each cell. Capsule ovoid to broad-ellipsoid, not lobed, 3-locular. Seeds usually 1 in each loculus, mucilaginous when wet.