Lemna minor L.

Indication of this species in Newfoundland (H. J. Scoggan 1978--1979) probably refers to Lemna turionifera.

A specimen in the Gray Herbarium from St. Pierre and Miquelon may represent Lemna minor or L. turionifera; its determination is questionable.

Roots to 15 cm, tip mostly rounded; sheath not winged. Stipes white, small, often decaying. Fronds floating, 1 or 2--5 or more, coherent in groups, ovate, scarcely gibbous, flat, 1--8 mm, 1.3--2 times as long as wide, margins entire; veins 3(--5) (if more than 3, outer ones branching from inner ones), greatest distance between lateral veins near or proximal to middle; papillae not always distinct (one near apex usually larger); lower surface very seldom slightly reddish (much less than on upper), coloring beginning from attachment point of root, upper surface occasionally diffusely reddish; air spaces 0.3 mm or shorter; distinct turions absent. Flowers: ovaries 1-ovulate, utricular scale with narrow opening at apex. Fruits 0.8--1 mm, laterally winged toward apex. Seeds with 8--15 distinct ribs, staying within fruit wall after ripening. 2n = 40, 42 (B), 50, 63, 126.

Fronds free floating, almost symmetrical, elliptical to ovate-obovate or oblong, 1.5-4 x 1.5-3 mm, flat on both surfaces, never gibbous and ± rounded apices, usually green above, solitary or several joined together by a hyaline stipe. Papillae absent or if present only at apex and above node with many meshes. Roots solitary with a wingless sheath, root cap obtuse, floral pocket lateral. Flowering specimens not seen.

All temperate and tropical regions. The Nepalese specimen seems to be referable to Lemna disperma Hegelm., but further critical studies are necessary.

St. Pierre and Miquelon; B.C., Ont., Que., Sask.; Ala., Ariz., Ark., Calif., Conn., Del., D.C., Fla., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis.; w Eurasia; Africa; Atlantic Islands; Australia (introduced), Australia; introduced, New Zealand (introduced).

Distribution: Temperate Eurasia, India, Iran, Pakistan Afghanistan, Africa, North America and New Zealand.

3000 m

Flowering (rare) late spring--early fall.

Mesotrophic to --eutrophic, quiet waters, in suboceanic, cool-temperate regions with relatively mild winters; 0--2000m.