Description from Flora of China
Herbs, annual or perennial. Leaves alternate, opposite, or whorled, often sessile; veins 1 or several and campylodromous. Inflorescences spicate, racemose, or rarely capitate. Calyx 5-lobed almost to base. Corolla tube tubular, base spurred; limb 2-lipped; lower lip convex, dilated toward center of upper lip, almost closed at throat, and making corolla personate, 3-lobed, densely glandular hairy; upper lip erect, 2-lobed. Stamens 4, anterior 2 longer; anthers anterior and posterior connivent in 2 pairs, locules parallel, divergent after dehiscence. Stigma apex often emarginate. Capsule ovoid or globose, apically dehiscing by irregular pores, valves irregular. Seeds numerous, flattened, often disclike with a broadly winged margin, rarely 3-angled and wingless or reniform and with a thickened margin.
About 100 species: northern temperate zones, mainly in Asia and Europe; ten species in China.