Description from Flora of China
Herbs (outside China), shrubs, or seldom small trees, perennial, terrestrial, not rhizomatous. Stems branched or simple. Leaves usually few, along stem, opposite, whorled, or rarely alternate, equal to subequal in a pair; leaf blade glabrous to densely pubescent, pilose, villous, or sericeous, base attenuate to cuneate, rarely to cordate. Inflorescences lax or dense, axillary or rarely cauliflorous, 1- to many-flowered cymes; bracts 2 or absent, opposite. Calyx actinomorphic or zygomorphic; 2-5(or 6)-lobed; lobes equal to unequal. Corolla white to yellow, occasionally green, orange, reddish, or purplish, zygomorphic or rarely actinomorphic, inside glabrous to pubescent; tube campanulate to salverform, funnelform, or cylindric, not swollen, usually much longer than limb; limb usually 2-lipped; adaxial lip 2-lobed, shorter than to slightly exceeding abaxial lip; abaxial lip 3-lobed, lobes equal or central lobe longer, apex rounded or obtuse, rarely acute. Stamens 2, adnate to abaxial side of corolla tube near middle, usually included; anthers basifixed to dorsifixed, coherent or free, thecae slightly divergent to divergent, confluent or not, dehiscing longitudinally; connective not projecting or apiculate; staminodes 2 or 3, adnate to adaxial side of corolla tube. Disc ringlike or rarely cupular. Ovary ovoid to oblong, 1-loculed; placentas 2, parietal, projecting inward, 2-cleft. Stigma 1, terminal, capitate to ovoid or obtriangular, undivided or sometimes 2-lobed. Berry fleshy to leathery, ovoid to oblong, slightly longer to shorter than calyx, indehiscent. Seeds unappendaged.
About 350-600 species: SE Asia, Pacific Islands; one species in China.