Herbs, perennial or annual, in fresh or brackish water, totally submerged or with floating leaves. Rhizome present or absent. Stems elongated or short, terete or compressed. Leaves alternate or basal occasionally opposite or subopposite, alike or dimorphic. Stipules free from leaves or adnate to leaf base and sheathing stems. Inflorescence a peduncled spike, with flowers lax or irregularly or whorled, terminal or axillary, emergent or submerged, enclosed by stipular sheaths when young. Plants monoecious, flowers small, ebracteate, sessile, bisexual, tetramerous, hypogynous. Perianth bract-like, free, usually 4 or absent. Stamens (1) 4, basally adnate to perianth segments, anthers sessile (mono- or) bithecous, extrorse, dehiscence longitudinal. Carpels (1-) 4, apocarpous, ovary unilocular with solitary ovule. Stigma sessile or subsessile. Fruit drupaceous. Embryo curved, exalbuminous.

5 genera, 114 species

Potamogeton nodosus