Description from Flora of China
Herbs or subshrubs. Stems solid. Leaves petiolate or subsessile, ovate to narrowly ovate, rarely linear to falcate, margin dentate, ± hairy or tomentose. Verticillasters regular or secund, in continuous or interrupted spikes, thyrses, or panicles; bracts and bracteoles linear to ovate. Calyx ovoid-tubular or campanulate, equally or subequally 5-toothed, with crystals. Corolla limb nearly 2-lipped, upper lip 3-lobed, lower lip entire, as long as to slightly longer than upper. Stamens 4, exserted, erect, free; filaments bearded at middle; anthers globose, 1-locular, cell apex dehiscent. Style apex 2-cleft, lobes subulate, equal or subequal. Nutlets ovoid to globose, slightly flattened, smooth.
About (40-)60 species: Africa, Asia; 16 species in China.