Description from Flora of China
Herbs or subshrubs. Leaves petiolate, dentate. Verticillasters 2-flowered, in terminal and axillary racemes; bracts persistent, somewhat lax or imbricate. Calyx campanulate, sparsely hairy, throat tufted hairy at each tooth sinus or pilose annulate; teeth 5, subequal or posterior tooth smaller. Corolla white, yellowish, or purple; tube funnelform to subcylindric, annulate; upper lip 2-lobed; middle lobe of lower lip flat; longer than circular lateral lobes. Stamens 4, exserted or rarely included, anterior 2 longer; filaments separate, glabrous, edentate; anther cells 2, divergent, apex confluent. Style filiform, apex 2-cleft; lobes subulate or ± linear, equal or unequal. Nutlets subglobose, glabrous.
About six species: China, Japan; five species in China.