Lemna valdiviana Phil.
Family: Araceae
Pale Duckweed
[Lemna cyclostasa (Ell.) C.H. Thompson,  more]
Lemna valdiviana image
USDA-NRCS PLANTS  
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."

Author: The Morton Arboretum

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.

©The New York Botanical Garden. All rights reserved. Used by permission.
From Flora of Indiana (1940) by Charles C. Deam
This species is local in the lake area and found in organic debris in completely stagnant water in swamps and ponds.