Description from Flora of China
Herbs erect perennials or very rarely annuals, ± villous to lanate. Leaves circular to ovate, corrugate, margin dentate. Verticillasters axillary, many flowered; bracts subulate, rarely absent. Flowers small. Calyx tubular, 5-10-veined; teeth 5-10, rigid, needlelike, equal or main teeth larger than accessory teeth, straight or spreading-reflexed. Corolla white or purple, rarely yellow, 2-lipped; tube included, glabrous or pilose annulate inside; upper lip straight, ± flat, apex emarginate or 2-lobed; lower lip spreading, 3-lobed, middle lobe apex emarginate. Stamens 4, small, included, anterior 2 longer; anther cells 2, divergent. Style included, apex 2-cleft. Nutlets triquetrous, ovoid, smooth, apex rounded.
About 40 species: temperate N Africa, Asia, and Europe, especially in the Mediterranean region; one species in China.