Erect or trailing, glabrous or villous herbs. Leaves opposite,
crenate-serrate to dentate. Flowers solitary in leaf axils or in cymes or
racemes. Calyx ribbed or winged, often 2-lipped and shortly toothed, usually
5-lobed. Corolla tube often dilated towards apex, limb bilabiate, lower lip
3-lobed, spreading, lobes subequal, upper lip erect, entire, emarginate or
2-lobed. Stamens 4, didynamous, anthers connivent in pairs. Ovary with short
coarse hairs, stigmas bilamellate. Capsules oblong, included in persistent
calyx, septicidal. Seeds numerous, scrobiculate.