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.
Plant: small aquatic plant Leaves: FRONDS floating on the water's surface or (rarely) submerged, single or mostly a few cohering in groups, ovate to obovate, 1-5mm long, 1.3-3 times as long as wide, flat and thin, without a green stalk but with a very small white stipe that often decays; margins entire; nerve 1, mostly prominent, longer than the extension of the air spaces or running through at least 3/4 of the distance between the attaching point of the root and the apex; papillae small, present or absent along the midline; anthocyanin absent; air spaces much smaller than 0.3 mm Flowers: very rare, 1-ovulate, the small utricular scale open on one side Fruit: 1.0-1.35 mm long, not winged. Seeds: with 15-29 ribs Misc: Mesotrophic, quiet waters; below 1800 m (6000 ft); May-Jul Notes: root up to 1.5 cm long, the sheath unwinged, the tip rounded to somewhat pointed; no distinct turions present REFERENCES: Landolt, Elias. 1992. Lemnaceae. Ariz.-Nev. Acad. Sci. 26(1)2.
Aquatic herb Flowers: occurring very rarely, lacking sepals and petals, with two stamens, surrounded by a membraneous scale open along one side. Fruit: bladder-like (utricle), thin-walled, 1 - 1.35 mm long, seeds having fifteen to 29 distinct ribs. Roots: to 1.5 cm long with a rounded to pointed tip. Plant body: not differentiated into stem and leaves, floating (rarely submersed), one to ten attached, 1 - 5 mm long, one and one-third to three times as long as wide, flattened, elliptic to narrow oblong, almost parallel-sided near the middle, usually asymmetric and somewhat pointed near base, single-veined, sometimes with a small projection along midvein. Air spaces in the plant body are much shorter than 0.3 mm and mostly close to the tip.
Similar species: Lemna minuta, Lemna obscura, and Lemna valdiviana are usually less than 1.5 mm wide and are veinless, single- or three-veined. Lemna minuta has a veinless to single-veined plant body that is rounded to inversely egg-shaped and almost symmetrical at the base. Lemna obscura has an often three-veined plant body that is rounded to inversely egg-shaped and purple beneath with a thin margin that tends to curl upward.
Flowering: spring to fall
Habitat and ecology: Quiet waters.
Occurence in the Chicago region: native
Etymology: Lemna is the Greek name for a water weed. Valdiviana means "of Valdivia, Chile."
Thallus flat or nearly so on both sides, usually smooth above, rather narrowly oblong, mostly 2.5-5 mm, commonly 1.5-3 times as long as wide, mostly 2-10 together, not anthocyanic, nerveless or indistinctly 1-nerved, the nerve often reaching more than 3/4 the distance from node to tip; spathe reduced, open; fr exserted, elongate-ovate, the persistent style obliquely terminal; seed solitary, oblong-ovoid, evidently ribbed; 2n=40. Widespread in the W. Hemisphere, and scattered in our range. (L. cyclostasa)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.