Description from Flora of China
Herbs, subshrubs, or shrubs, aromatic. Leaves petiolate, dentate. Verticillasters 6(-10)-flowered, in terminal, pedunculate thyrses or panicles; bracts early deciduous, petiolate, margin entire, rarely longer than flowers. Flowers white; pedicel straight, apex recurved. Calyx ovoid to campanulate, declined in fruit, glandular outside, glabrous or occasionally villous at throat inside, limb 2-lipped; upper lip 3-toothed, middle tooth circular to obovate, margin winged, decurrent, lateral teeth shorter; lower lip 2 toothed, teeth narrower, apex acuminate to spinescent, sometimes approximate. Corolla tube slightly shorter than calyx or rarely exserted, not hairy annulate inside, dilated, obliquely campanulate at throat; limb 2-lipped, upper lip subequally (3- or) 4-lobed; lower lip somewhat elongated or not, declined, margin entire, flat or slightly concave. Stamens 4, exserted, declined on lower corolla lip, anterior 2 longer; filaments free or anterior 2 connate at base; anthers ovoid-reniform, 1-locellate. Style longer than stamens, 2-cleft at apex; lobes subequal, subulate or flat. Nutlets ovoid or subglobose, smooth or glandular foveolate, viscid when moist, with a white basal areola.
About 100-150 species: temperate regions worldwide, especially in Africa and South America; five species in China.