Rep. (Annual) Missouri Bot. Gard. 9:28. 1898.
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
Phenology: Flowering (rare) summer�early fall.
Habitat: Eutrophic, quiet waters, in warm-temperate to subtropical regions with mild winters
Elevation: 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.