Perennials, with stolons, without well-developed caudices, stout rhizomes, or persistent taproots. Stems branching sympodially; flowering stems arising singly from slender stolons, often creeping and rooting at lower nodes. Inflorescences terminal. Flowers usually sessile, solitary or in few-flowered clusters. Stigma lobes free, recurved, linear or oblong. Seed coat alveolate, with simple and shallow or spongy and complex hexagonal pits.

Eighteen species: North America, Asia; 16 species in China.