a genus of aquatic plants of the family Lemnaceae. It has a single species—great duckweed (Spirodella polyrrhiza) —a perennial plant with a rounded modified stem, or frond, which floats on the surface of the water and bears a bundle of small roots. The unisexual flowers do not have a perianth and are gathered into an inflorescence containing one pistillate and one staminate flower. The fruit is monospermous and indehis-cent. Great duckweed rarely blossoms. It propagates by branching of the frond. The plant grows in the northern hemisphere; it is found throughout the USSR except in the Crimea and Middle Asia, growing in stagnant and slow-moving waters. Great duckweed serves as feed for pigs, geese, ducks, and fowl.