Pistia(redirected from Water-lettuce)
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a genus of plants of the family Araceae. There is one species, the water lettuce (P. stratiotes), which is a free-floating or sometimes rooted aquatic plant with rosettes of wedge-shaped, downy, light green leaves that fold up at night. New leaf rosettes develop from the axillary buds. The flowers are unisexual and naked; they are in small spadices surrounded by a whitish spathe. In the lower part of the spathe there is one pistillate flower with several male flowers above it. (Each male flower consists of two fused stamens.) The water lettuce is found in the tropics and subtropics of both hemispheres, mainly in freshwaters. It is cultivated in fishponds and aquariums. In China the plants are used as swine feed.