Lemna valdiviana

Lemna valdiviana is a species of duckweed known by the common name Valdivia duckweed. It is native to much of the Americas. It is a minute flowering plant which grows in mats on the surface of calm bodies of freshwater. The individual plant is a flat, translucent, pale green oval body 2 to 4 millimeters long. There is a longitudinal vein visible under magnification and microscopy. The body produces a root which may exceed a centimeter in length, and a tiny, ephemeral flower which is often encapsulated in a membrane. The plant often grows in clusters of two to seven individuals....read more on Wikipedia.