Description from Flora of China
Plants small shrubs, rarely herbs. Verticillasters 2-10-flowered, in crowded terminal spikes; bracteoles small or absent. Flowers short pedicellate or subsessile. Calyx ovoid-tubular to tubular, slightly dilated in fruit, straight, 13-15-veined, 2-lipped; upper lip entire, protracted into an appendage; lower lip equally (2-)4-toothed, teeth narrower than those of upper lip. Corolla blue or purple; tube exserted, throat ± dilated; limb 2-lipped, upper lip 2-lobed, lower 3-lobed. Stamens 4, included, anterior 2 longer; anther cells apically confluent. Style inserted at ovary base, apex 2-cleft, lobes flattened, ovate, connate. Nutlets smooth, shiny, each with a basal-dorsal areole.
About 28 species: China, India, Pakistan; Africa, SW Asia, Atlantic Islands, Europe; two species are cultivated in China.