Description from Flora of China
Herbs perennial. Leaves pinnatifid to subentire. Verticillasters 6-flowered, in terminal ovoid or ovoid-globose spikes; bracts broad, membranous, margin ciliate, overlapping; bracteoles minute or absent. Pedicel very short or absent. Calyx tubular-campanulate, ± flattened dorsiventrally, irregularly 10-veined, netted between veins, 2-lipped, base hairy, throat glabrous; upper lip flat, truncate, shortly 3-toothed; lower lip 2-cleft to 1/2 of lip, teeth lanceolate, mouth closed in fruit. Corolla tube gradually dilated on 1 side, exserted, throat slightly constricted, scaly annulate inside, limb 2-lipped; upper lip straight, galeate, margin entire; lower lip 3-lobed, middle lobe largest, concave, denticulate; lateral lobes oblong, reflexed. Stamens 4, anterior 2 longer, ascending to underside of upper lip, parallel, free; filament apex dentate; anther cells 2, divaricate. Ovary glabrous. Style glabrous, apex equally 2-cleft, lobes subulate. Nutlets brown, subglobose, ovoid to oblong, glabrous, smooth or tuberculate, apex rounded.
About seven broadly defined species (15 by some authors): Africa, Asia, Europe, North America; four species (one cultivated) in China.