Description from Flora of China
Herbs, perennial, epipetric or terrestrial, rhizomatous, stemless [or stemmed]. Leaves few to many, along stem, then opposite, sometimes spirally arranged or basal (in China), equal to subequal in a pair; leaf blade villous to puberulent, hairs unicellular, long, seldom short or glandular, base attenuate to cordate. Inflorescences lax, axillary, sometimes umbel-like, 1- to many-flowered cymes; bracts 2, opposite. Calyx actinomorphic, 5-sect from near base, rarely 5-lobed from middle; segments equal to slightly unequal. Corolla white, blue, or purple, zygomorphic, inside densely puberulent or glandular puberulent to glabrous, outside campanulate to broadly campanulate, not swollen, longer than to nearly equalling limb, 4-10 mm in diam.; limb distinctly or indistinctly 2-lipped; adaxial lip 2-lobed, shorter than abaxial lip; abaxial lip 3-lobed, lobes equal or subequal, apex rounded. Stamens 2, adnate to abaxial side of corolla tube near base, included; anthers dorsifixed, coherent, thecae divaricate, confluent at apex, dehiscing longitudinally from arcuate slits; connective not projecting; staminodes 2 or 3, adnate to adaxial side of corolla tube. Disc inconspicuous. Ovary oblong, 1-loculed; placentas 2, parietal, projecting inward, 2-cleft. Stigma 1, terminal, capitate, undivided. Capsule straight in relation to pedicel, narrowly oblong, much surpassing calyx, dehiscing loculicidally to base; valves 2, spirally twisted. Seeds unappendaged.
About 20 species: Australia, China, E India, Malaysia, Myanmar, Philippines, Polynesia, Vietnam; three species in China.