Vallisneria

Vallisneria 

a genus of perennial plants of the Hydrocharitaceae family. They are underwater grasses with large creeping roots and linear leaves. There are six species, distributed in the fresh waters of the tropical, subtropical, and temperate regions of both hemispheres. Best known is tape grass (V. spiralis), which grows in reservoirs at depths up to 1 m. In the USSR it is found in the mouths of the Dunai, Dnieper, and Volga and in lakes in the Caucasus, Middle Asia, and the Far East. The flowers of tape grass are diclinous and develop under water, but emerge on the surface for pollination. The pollinated flower again sinks into the water, where the fruit ripens. Tape grass serves as food for fish and waterfowl and is often planted in aquariums.