Description from Flora of China
Herbs, or shrubs, annual or perennial, erect, sometimes with long rhizomes. Stems basally woody, narrowly 4-winged or terete and wingless. Leaves opposite, decussate, sessile or subsessile; leaf blade mostly lanceolate, margin entire or serrate. Racemes terminal; bracts foliaceous. Flowers opposite, few. Pedicel short. Bracteoles 2, at pedicel apex. Calyx tube broadly campanulate, 5-veined, somewhat 2-lipped; lobes 5, 2 upper lobes shorter than other lobes, margin entire. Corolla 2-lipped, slightly longer than calyx; tube funnelform; lower lip usually nearly as long as upper, 3-lobed, lobes subequal, with 2 raised folds; upper lip 2-lobed, lobes arched, recurved at margin. Stamens didynamous; filaments inserted below middle of corolla tube; anthers 2-loculed, dorsifixed; anther locules parallel, longitudinally dehiscent, densely white villous. Ovary usually ovoid, 2-loculed, densely hirsute. Style densely villous; stigma 2-lobed. Capsule black-brown. Seeds numerous, small; seed coat scrobiculate-reticulate or seed enclosed in large bladdery loose hyaline reticulated appendage.
* Five species: endemic to China.