Lemna minima Philippi; L. minuscula Herter

Roots to 1.5 cm, tip rounded to pointed; sheath not winged. Stipes white, small, often decaying. Fronds floating, 1 or 2--few, coherent in groups, obovate, flat to thickish (but not gibbous), 0.8--4 mm, 1--2 times as long as wide, margins entire; veins 1, sometimes indistinct, very rarely longer than extension of air spaces, not longer than 2/3 of distance between node and apex; with or without small papillae along midline; anthocyanin absent; largest air spaces much shorter than 0.3 mm; turions absent. Flowers: ovaries 1-ovulate, utricular scale open on 1 side. Fruits 0.6--1 mm, not winged. Seeds with 12--15 distinct ribs. 2n = 36 (U), 40 (U), 42 (G).

Flowering (very rare) late spring--early fall. Mesotrophic to eutrophic, quiet waters in temperate to subtropical regions with relatively mild winters; 0--2600 m; Ala., Ariz., Ark., Calif., Colo., Fla., Ga., Ill., Ind., Kans., Ky., La., Mich., Mo., Nebr., Nev., N.Mex., Ohio, Okla., Oreg., Tenn., Tex., Utah, Wash., W.Va., Wyo.; Mexico; West Indies; Central America; South America; introduced, Eurasia (introduced).

I know of no specimens of Lemna minuta from Mississippi, but the species is to be expected there.