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(pondweed), a genus of perennial aquatic herbs of the family Potamogetonaceae. The alternate leaves are petiolate or sessile and submerged or floating; they range in shape from almost round to threadlike. The inconspicuous and bisexual flowers are in spikes that are usually above the water. The perianth consists of four round valvate lobes; there are four stamens, with no filaments. The fruit consists of four drupaceous lobes. The plants are usually anemophilous.
There are approximately 100 species of pondweed, distributed throughout the world in standing or slow-flowing fresh or, less often, slightly salty waters. The USSR has more than 40 species, which include the broad-leaved pondweed (P. natans), the perfoliate pondweed (P. perfoliatus), the curled pondweed (P. crispus), and the shining pondweed (P. lucens). Small animals that are eaten by fish live on the underwater parts of the plants; fish spawn in pondweed thickets. Some species are eaten by waterfowl. Pondweed thickets often hamper the movement of small boats.