Lemna punctata G. Meyer, Prim. Fl. Esseq., 262. 1818; Spirodela oligorrhiza (Kurz) Hegelmaier

Roots (1--)2--7(--12), to 7 cm, all perforating scale. Fronds obovate, flat or gibbous, 1.5--8 mm, 1.5--2 times as long as wide, apex mostly pointed, upper surface without red spot; veins (3--)5--7; distinct turions absent. Flowers: ovaries 1--2-ovulate. Fruits 0.8--1 mm, laterally winged to apex. Seeds with 10--15 distinct ribs. 2n = 40, 46, 50...

Flowering (rare) summer–early fall. Eutrophic, quiet waters, in warm-temperate to subtropical regions with mild winters; 0--900 m; introduced; Ala., Ariz., Ark., Calif., D.C., Fla., Ga., Ill., Ky., La., Miss., Mo., N.C., Okla., Oreg., Pa., S.C., Tenn., Tex., Va., Wash.; South America; Asia; Africa; Atlantic Islands; Pacific Islands; Australia.