Description from Flora of China
Herbs perennial, villous, rhizomatous or stoloniferous. Stems erect or ascending. Leaves widely spaced, smaller or absent basally, overlapping upward, sessile or subsessile; leaf blade subcircular to reniform-ovate, papery. Verticillasters apical, obscured by upper leaves; bracts small, linear-subulate. Calyx tubular, straight or slightly curved, 15-veined, tube villous annulate inside, ± 2-lipped, upper lip 3-toothed, lower lip 2-toothed. Corolla tubular, gradually dilated at apex, exserted, usually resupinate, 2-lipped; upper lip (apparent lower lip when corolla resupinate) straight, 2-lobed; lower lip (apparent upper lip when corolla resupinate) 3-lobed, middle lobe slightly cuculate, lateral lobes oblong to oblong-ovate. Stamens 4, didynamous, anterior 2 (posterior when corolla resupinate) shorter, included, posterior 2 sometimes long exserted; anther cells 2, divergent. Ovary glabrous. Style slender, apex 2-cleft. Nutlets oblong-ovoid, smooth, base small umbonate.
About five species: China, India; all in China.