Description from Flora of China
Herbs aromatic, annual. Leaves dentate. Verticillasters 2-flowered, in terminal and axillary secund racemes; bracts broadly ovate to subcircular. Flowers pedicellate. Calyx campanulate, 10-veined, straight in flower, enlarged, spreading or pendulous, swollen on 1 side in fruit, throat pilose annulate, limb 2-lipped, upper lip 3-toothed, with middle tooth smallest, lower lip 2-toothed, teeth lanceolate. Corolla white to purple-red, campanulate, throat oblique; limb nearly 2-lipped, upper lip emarginate; lower lip 3-lobed, lateral lobes smaller than middle, similar to upper lip. Stamens 4, subequal or anterior 2 longer, erect, separate; anther cells 2, parallel, becoming divergent or divaricate. Style included, apex 2-cleft; lobes subequal, subulate. Nutlets subglobose, netted.