Lemna cyclostasa (Elliott) C. H. Thompson; L. torreyi Austin

Roots to 1.5 cm, tip rounded to pointed; sheath not winged. Stipes white, small, often decaying. Fronds floating or (rarely) submersed, 1 or 2--few, coherent in groups, ovate to lanceolate, flat, thin, 1--5 mm, 1.3--3 times as long as wide, margins entire; veins 1, mostly prominent, longer than extension of air spaces, or running through at least 3/4 of distance between node and apex; with or without small papillae along midline of upper surface; anthocyanin absent; largest air spaces much shorter than 0.3 mm; turions absent. Flowers: ovaries 1-ovulate, utricular scale open on 1 side. Fruits 1--1.35 mm, not winged. Seeds with 15--29 distinct ribs. 2n = 40, 42.

Flowering (very rare) spring--fall. Mesotrophic, quiet waters in temperate to tropical regions; 0--2000 m; Ala., Ariz., Ark., Calif., Conn., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mass., Mich., Miss., Mo., Mont., Nebr., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va., Wyo.; Mexico; West Indies (Bermuda); Central America; South America.

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