Description from Flora of China
Herbs annual or perennial. Verticillasters 6-10-flowered, in terminal secund thyrses or panicles; bracts small, deciduous. Calyx ovoid-campanulate to campanulate, declined in fruit, somewhat elongated, slightly constricted at throat; teeth 5, posterior 1 or 3 larger; tube hairy outside, throat glabrous inside. Corolla tube included or slightly exserted, campanulate, dilated at throat, limb 2-lipped; upper lip 3-lobed, middle lobe larger, entire or apex sometimes emarginate; lower lip slightly longer, margin entire, flat, somewhat concave. Stamens 4, anterior 2 longer, declined; filaments separate, edentate; anthers subglobose, 1-locellate. Style clavate-capitate, 2-cleft at apex; lobes subulate, subequal. Disc ringlike or swollen as a finger in front. Nutlets obovoid, dorsiventrally flattened, smooth.
About six or seven species: Africa, Asia, Australia; one species in China.