Description from Flora of China
Shrubs or perennial herbs, decumbent to erect, with cystoliths. Leaves opposite, petiolate; leaf blade margin entire or dentate. Inflorescences of axillary or terminal bracteate spikes to panicles of spikes or of variously disposed cymes (these sometimes clustered in leaf axils); bracteoles usually 4, in 2 to rarely more pairs, distinct or connate, inner pair sometimes partially adnate to outer pair, forming an involucre enclosing 1 or sometimes more flowers. Calyx small, usually obscured by bracteoles, scarious or membranous, 5-lobed; lobes equal or subequal in length. Corolla rose-pink, purplish, or whitish, resupinate 180° by torsion of tube; tube subcylindric to expanded distally into a narrow throat; limb 2-lipped; lower lip (in upper position) shallowly 3-lobed; upper lip (in lower position) subentire or shallowly 2-lobed; lobes ascending cochlear in bud. Stamens 2, inserted near apex of corolla tube, exserted from mouth of corolla; anthers 1-thecous; theca muticous. Ovary with 2 ovules per locule; style exserted from mouth of corolla; stigma 2-lobed, lobes equal or unequal. Capsule stalked, 2-4-seeded; retinacula present. Seeds smooth or ornamented.
About 150 species: Old World; three species in China.
(Authors: Hu Jiaqi (胡嘉琪 Hu Chia-chi), Deng Yunfei (邓云飞); Thomas F. Daniel)