Description from Flora of China
Herbs, rarely basally woody. Stems simple or branched at base. Leaves alternate, large, often crowded below, margin entire or toothed. Flowers in terminal, often secund racemes. Calyx 5-lobed; lobes imbricate. Corolla oblique, tubular-campanulate, often constricted beyond ovary, somewhat ventricose; limb slightly 2-lipped; lower lip 3-lobed, middle lobe longer than lateral lobes; upper lip lobes much reduced, emarginate. Stamens 4, didynamous, included; anthers touching in pairs, locules divaricate, apically confluent. Style 2-lobed. Capsule ovoid, septicidal. Seeds numerous, oblong to subovoid, small, ribbed; seed coat scrobiculate-reticulate.
About 25 species: Asia, Europe; one species cultivated in China.