Annual or perennial herbs, rarely shrubs; branches with simple hairs and often, sessile glands. Leaves petiolate, opposite; margin entire, or crenate to deeply lobed. Inflorescences spike-like, of cymose clusters (often reduced to 1 or 2 flowers) in axils of leaves or bracts, forming pseudowhorls. Calyx 2-lipped, 13–15-nerved, adaxial lip 3-toothed to subentire, abaxial lip deeply 2-lobed; corolla 2-lipped, the adaxial lip erect, c. hooded, scarcely 2-lobed, abaxial lip 3-lobed, with median lobe broad and 2 lateral lobes narrow; stamens 2, fertile, locules separated by elongated connective, one locule abortive, staminodes 2, minute, sometimes absent; stigma unequally 2-fid. Mericarps smooth.
About 700 species, in tropical to temperate regions; 1 species native and 5 naturalised in Australia.