Description from Flora of China
Herbs, perennial or suffrutescent, rarely annual. Leaves opposite or rarely upper ones alternate. Cymes axillary or terminal and solitary, or inflorescences lateral thyrses, racemose, spicate, or subcapitate, usually pedunculate. Calyx 5-lobed. Corolla usually 2-lipped; lower lip shorter than upper lip, 3-lobed, middle lobe flattened forward, lateral lobes suberect; upper lip 2-lobed, lobes suberect. Stamens 4, somewhat didynamous, included to exserted, adnate to corolla tube; anther locules confluent; staminode 1, small. Disc present. Style as long as or longer than ovary, slightly shorter in S. urticifolia; stigma often small. Capsule septicidal. Seeds numerous.
About 200 species: temperate Asia, Europe (mostly Mediterranean), North America; 36 species in China.