Description from Flora of China
Herbs, perennial, with underground rhizomes. Stem erect, with white pith becoming hollow. Leaves simple, opposite, obovate,
entire, undulate to deeply pinnatifid. Inflorescence of sessile 6-flowered whorls; bracts and bracteoles lanceolate, shorter than flowers. Calyx 5-lobed, persistent. Corolla yellow-green, yellow, or purple; lobes 5, imbricate, bilabiate, upper lip 4-lobed, lower lip entire and recurved at anthesis. Nectary of compact glandular hairs, forming a bulge at base of corolla tube. Stamens 5, inserted in corolla tube; anthers introrse. Ovary 3-5-locular; ovule 1 per locule sometimes aborted, pendulous; style filiform; stigmas discoid, 3-5-lobed. Fruit a drupe, subglobose to pyriform, ± fleshy; pyrenes 2-4, black, with a thick stony endocarp, sometimes ribbed; endosperm fleshy, embryo small.
About six species: C and E Asia, North America; three species in China.