Duckweed
Duckweed, the common name for several tiny plants that are among the smallest flowering plants known. Duckweed grows on the surface of ponds and slow-moving streams and is eaten by waterfowl, fish, and other animals. The duckweed does not have separate leaves or a stem. Instead, it has a frond, a twig-like shoot, about 1/8 inch (3 mm) long, that bears short, hair-like roots and extends downward in the water.
Most duckweeds belong to the genus Lemna of the family Lemnaceae.