Perennials. Stems erect, quadrangular, basally woody. Leaves opposite, petiolate, simple. Inflorescences axillary or from basal woody part of stem, cymose, few to many flowered or flower solitary from axil of upper leaves; bracts small, membranous. Calyx tubular, becoming urceolate in fruit, apex truncate and shallowly 5-lobed. Corolla funnelform; limb sublabiate; lower lip 3-lobed; upper lip 2-lobed; lobes orbicular. Stamens 4, didynamous, inserted basally on corolla tube; anther locules divergent, apices confluent. Ovary conical or cylindric. Style filiform; stigma 2-lamellate. Capsule loculicidal, enclosed in calyx. Seeds numerous, ellipsoid, reticulate.

About 10 species: S and SE Asia; one species in China.