Roots to 2.5 cm (sometimes not developed), tip pointed; sheath not winged. Green stalks 2--20 mm. Fronds submersed (except when flowering or fruiting), 3--50, coherent and very often forming branched chains, narrowly ovate, flat, thin, 3--15 mm (excluding stalk), 2--3.5 times as long as wide, base suddenly narrowed into green stalk, margins denticulate distally; veins (1 or) 3, lateral veins only in proximal part of frond; papillae absent; anthocyanin often present; air spaces shorter than 0.3 mm; turions absent. Flowers: ovaries 1-ovulate, utricular scale with narrow opening at apex. Fruits 0.6--0.9 mm, laterally winged toward apex. Seeds with 12--18 distinct ribs, staying within fruit wall after ripening. 2n = 40, 42, 44, 60, 63, 80. Flowering (rare) late spring--summer. Mesotrophic, quiet waters rich in calcium, in cool-temperate regions; 0--3000 m; Alta., B.C., Man., N.B., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; nearly worldwide, except arctic and antarctic regions and South America; in warm regions only in mountains. The report of Lemna trisulca in Florida is dubious because the climate is too warm. The species may be temporarily introduced there by birds.

Plant: small aquatic plant Leaves: FRONDS submerged, 3-50 cohering and very often forming branched chains, narrowly ovate, 3-15 mm long (without stalk), 2-3.5 times as long as wide, flat and thin, narrowed at the base into a 2-20 mm long green stalk; margins distally denticulate; nerves (1-)3, the laterals only in the lower part of the frond; papillae absent; anthocyanin often present; air spaces smaller than 0.3 mm Flowers: rare (the flowering fronds floating on the water's surface), 1-ovulate, the small utricular scale with a narrow opening at the top Fruit: 0.6-0.9 mm long, laterally winged towards the top SEEDS: with 12 to 18 distinct ribs Misc: Mesotrophic, quiet waters rich in calcium; 2100-2700 m (7000-9000 ft); May-Aug Notes: root up to 2.5 cm long (sometimes not developed), the sheath unwinged, the tip pointed; turions absent REFERENCES: Landolt, Elias. 1992. Lemnaceae. Ariz.-Nev. Acad. Sci. 26(1)2.