VAL'LISNE'RIA (Neo-Lat., named in honor of Antonio Vallisneri, an Italian botanist of the eighteenth century). A genus of small, stemless, aquatic plants, with grass-like leaves, belonging to the natural order Hydrocharidaceæ, and found in the warm parts of both hemispheres. They generally grow in running waters. Vallisneria spiralis is particularly celebrated on account of its peculiar process of fecundation. The flowers of the female plants rise to the surface of the water by uncoiling their long spirally twisted stalks; the flowers of the male plants become detached, having previously grown on short spikes at the bottom of the water, and expand, floating about upon the surface. After fecundation, the female flowers return under the water by the recoiling of their stalks and the fruit is ripened under water. The plant is found in ditches and bogs in Italy, Southern France, and the United States, where it is called wild celery, and is famous as the food of the canvas-back duck.