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.
Plant: small aquatic plant Leaves: FRONDS obovate, 1.5-8 mm long, 1.5-2 times as long as wide, flat or gibbous, without red spot on the upper surface; nerves 3-7 Flowers: rare, 1-2-ovulate, stamens 2, 4-locular Fruit: 1.0-1.5 mm long, laterally winged to the top; SEEDS 1-3, with 12-20 distinct ribs Misc: eutrophic, quiet waters; 2100 m (ca. 7000 ft); Jul-Sep Notes: roots (1-)2-7(-12), to 7 cm long; no distinct turions present REFERENCES: Landolt, Elias. 1992. Lemnaceae. Ariz.-Nev. Acad. Sci. 26(1)2.
Like a small version of no. 1 [Spirodela polyrhiza (L.) Schleid.]; thallus 2.5-5 mm, half to 3/4 as wide, obscurely 3-5-nerved; roots 2-5; seed solitary; 2n=40, 50. Quiet water; widely scattered in warm regions, rare and irregular with us. (S. oligorhiza)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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