Description from Flora of China
Subshrubs or annual or perennial herbs, lanate or villous. Leaves petiolate. Verticillasters 2- to many flowered, in terminal spikes; floral leaves reduced to bracts. Flowers small. Calyx tubular-campanulate, equally or subequally 5-toothed or slightly 2-lipped, 5-10-veined; teeth straight, apex spiny. Corolla yellow, 2-lipped; tube included; upper lip straight, nearly flat, entire to 2-lobed; lower lip spreading, 3-lobed; middle lobe large, apex emarginate. Stamens 4, included, didynamous, anterior 2 longer, with deformed anthers, posterior 2 shorter, with 2-celled anthers; anther cells divaricate. Style included, apex unequally 2-cleft. Nutlets triquetrous, ovoid, smooth, apex obtuse to rounded.
Approximately 100 species: temperate Asia and Europe, two species in China.