Perennial, biennial or annual herbs or small shrubs with square stems. Lvs usually opposite, entire to pinnatisect. Fls in cymes in the axils of upper lvs or bracts, and sometimes forming terminal racemes or panicles, occasionally solitary. Calyx with 5 equal lobes. Corolla tube short, ± globose; limb with 5 lobes, usually 2-lipped but sometimes almost regular. Fertile stamens 4, included or exserted; staminode usually 1 and scale-like, occasionally 0. Capsule globose to ovoid, septicidal. Seeds numerous, ovoid, rugose, small; wing 0.