Description from Flora of China
Plants annual or perennial, herbaceous or subshrubby. Leaves short petiolate or subsessile; leaf blade abaxially glandular. Verticillasters scattered in leaf axils or crowded in a terminal capitulum; floral leaves as large as stem leaves or reduced. Calyx narrowly cylindric, straight to slightly curved, 13-veined, villous annulate at throat, obscurely 2-lipped, upper lip 3-toothed, lower lip 2-toothed; teeth subequal, close together, rarely divergent following anthesis. Corolla limb 2-lipped; upper lip straight, margin entire, apex emarginate; lower lip spreading, 3-lobed, middle lobe narrower than suborbicular lateral lobes, apex emarginate. Anterior stamens fertile, reaching upper corolla lip, posterior stamens rudimentary, short, or absent; anther cells linear, 2 or only 1 developed, the other reduced to an appendage or absent. Style apex unequally 2-cleft, posterior lobe short. Nutlets ovoid, smooth.
About 25-30 species: Africa, Asia, Europe; four species in China.