Leaves submerged or floating, alternate or imperfectly opposite, toothed or entire. Flowers ebracteate, small, tetramerous, actinomorphic, spicate in dense or interrupted ovoid or cylindric spikes (submerged water pollinated, emergent on a peduncle wind pollinated). Perianth segments concave, smooth, obovate. Stamens 4, sessile or sub-sessile. Fruitlets drupaceous, coriaceous, more or less compressed, one seeded, smooth or ornamented with warts, crests or short spines; embryo uniform or spiral.