Description from Flora of China
Shrubs, erect or scandent, occasionally parasitic, usually stellate tomentose. Leaves opposite, rarely subopposite; petiole short; leaf blade margin entire or denticulate. Flowers axillary, solitary, paired, or in racemes. Bracteoles 2, inserted on pedicels. Calyx campanulate, rarely cylindric-ovate, outside stellate hairy, regular or somewhat 2-lipped; lobes 2 or 5. Corolla tube somewhat incurved; limb 2-lipped; lower lip as long as or shorter than upper lip, 3-lobed, patent; upper lip 2-lobed, concave. Stamens 4, didynamous, somewhat exserted or included, inserted at base of corolla tube; filaments glabrous; anther locules 2, orbicular, pilose; staminode absent. Ovary ovoid, hairy, 2-loculed; ovules numerous, linear-oblong. Style elongated; stigma simple. Capsule ovoid to ovoid-globose, loculicidal. Seeds linear; seed coat reticulate, membranous winged.
About 11 species: mountainous areas of subtropical E Asia; eight species in China.