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.