Description from Flora of China
Herbs, shrubs, or small trees, with cystoliths. Leaves opposite; leaf blade large, margin entire or obscurely crenate. Inflorescences in terminal thyrses or axillary cymes, pedunculate; bracts small; bracteoles small or absent. Calyx deeply 5-lobed; lobes equal to unequal. Corolla tubular, slightly curved (arched); limb subequally 5-lobed or 2-lipped; lower lip 3-lobed, lobes ascending cochlear in bud; upper lip 2-cleft. Stamens 2, inserted at middle or basal portion of tube, included or sometimes slightly exserted beyond corolla lip; anthers 2-thecous; thecae equal, base divaricate and muticous; staminodes 2, small. Ovary usually glabrous; stigma subentire. Capsule linear, 4-angled, basal portion solid but lacking a conspicuous basal stalk; retinacula present, 8-16-seeded. Seeds lenticular, glabrous or pubescent.
About 15 species: mainland Asia; two species in China.
(Authors: Hu Jiaqi (胡嘉琪 Hu Chia-chi), Deng Yunfei (邓云飞); Thomas F. Daniel)