Wolffia

right|thumb|Close-up of floating aquatic plants: Spirodela polyrrhiza and [[Wolffia globosa; the very tiny Wolffia plants are under long.]]

Wolffia is a genus of aquatic plants with a cosmopolitan distribution. They include the smallest flowering plants on Earth. Commonly called watermeal or rootless duckweed, these aquatic plants resemble specks of cornmeal floating on the water. They often float together in pairs or form floating mats with related plants, such as Lemna and Spirodela species.