Plants with young vegetative parts heavily mucilaginous. Leaves all floating, long petiolate; leaf blade broadly elliptic, venation radiate, margin entire. Flowers anemophilous, usually long pedunculate; perianth not showy. Sepals linear-oblong to narrowly ovate. Petals narrowly oblong, lacking basal auricles. Stamens 12--36(--51), opposite both sepals and petals. Pistils 6--18; ovules (1--)2; stigmas linear-decurrent. Fruit slightly to strongly fusiform; seeds ovoid, lacking tubercles.

One species: temperate and montane tropics, mainly in the N hemisphere, but absent from W Asia and Europe.