Description from Flora of China
Herbs. Leaves petiolate, dentate. Verticillasters in terminal racemes; bracts sessile, circular, ovate to lanceolate, apex caudate-mucronate, sometimes brightly colored. Pedicel slender, hairy. Calyx campanulate in flower, tubular or urceolate-tubular in fruit, 10-veined, transversely many veined, pitted in fruit, 2-lipped; upper lip 3-toothed, middle tooth very large; lower lip entire, occasionally emarginate. Corolla white or reddish; throat very wide, not hairy annulate inside; limb 2-lipped, upper lip truncate or 4-lobed; lower lip longer than upper lip, margin entire, navicular. Stamens 4, exserted; filaments free, posterior 2 1-dentate at base; anthers 1-locellate. Style longer than stamens, apex unequally 2-cleft, lobes subulate. Nutlets oblong or ovoid, smooth or inconspicuously tuberculate.
About 8-10 species: Asia, two species in China.