Herbs annual, biennial, or perennial, smooth, glabrous. Stems prostrate or decumbent, ribbed, striate. Leaves alternate, petiolate; leaf blade flattened, margin entire or subentire. Flowers solitary or in 2- or 3-flowered glomerules arranged in terminal spikes on upper part of branches, without bractlets, perfect, fused at base and falling together at utricle maturity. Perianth urceolate, 5-parted, mostly herbaceous, more rarely petaloid, united and hardened at base; segments erect or infolded, longitudinally keeled abaxially. Stamens 5, perigynous; filaments subulate, united proximally into a glandular disk; anthers oblong. Stigmas 2 or 3(-5), stigmatic surface papillate. Utricle proximally adnate to perianth; pericarp succulent or hardened distally. Seed horizontal, depressed globose; testa leathery, lustrous, free from pericarp; embryo annular or subannular; perisperm copious.

About ten species: N Africa, SW Asia, Europe; one species (introduced) in China.