2. LÉMNA, L. Duckweed. Duck's-meat.
Flowers produced from a cleft in the margin of the frond, usually three together surrounded by a spathe; two of them staminate, consisting of a stamen only; the other pistillate, of a simple pistil; the whole therefore imitating a single diandrous flower. Ster. Fl. Filament slender; anther 2-celled, didymous; the cells dehiscent transversely; pollen-grains large, spherical, muricate. Fert. Fl. Ovary 1-celled; style and truncate or funnel-shaped stigma simple. Ovules and seeds 1–7.—Fronds 1–5-nerved, producing a single rootlet beneath (which is destitute of vascular tissue), proliferous from a cleft in the margin toward the base, and at length stipitate; the tissue abounding with bundles of rhaphides. (An old Greek name of uncertain meaning.)
[*] Ovule solitary, orthotropous or nearly so; frond 1–3-nerved, thin.
[+] Fronds oblong, stalked at base, remaining connected.
1. L. trisúlca, L. Fronds oblong to oblong-lanceolate (6–9´´ long), attenuate at base into a slender stalk, denticulate at the tip, very obscurely 3-nerved, often without rootlets, usually several series of offshoots remaining connected; spathe sac-like; seeds ovate, amphitropous, with small round operculum.—Ponds and springy places, N. Scotia to N. J., west to the Pacific. (Eu.)
[+][+] Fronds oblong to elliptical or round-ovate, sessile, soon separating.
2. L. Valdiviàna, Philippi. Fronds elliptic-oblong, small (about 1´´ long), rather thick, usually somewhat falcate, obscurely 1-nerved; spathe broad-reniform; utricle long-ovate, pointed by the long style; seed orthotropous, oblong, with a prominent acute operculum. (L. Torreyi, Austin.)—Pools, N. J. and southward, westward across the continent. (S. Am.)
3. L. perpusílla, Torr. Fronds obovate or roundish-obovate, oblique (1–1½´´ long), obscurely 3-nerved; utricle ovate; style rather long; seed orthotropous, ovate or oval, obtuse, with scarcely apiculate operculum.—N. Y. and N. J., west to Mich. and Wisc.—Var. trinérvis, Austin, has larger, distinctly 3-nerved fronds, and an unequally cordate seed.
4. L. mìnor, L. Fronds round- to elliptic-obovate (1–2½´´ in diameter), rather thick, very obscurely 3-nerved; spathe sac-like; utricle short-urn-shaped, tipped with a short style; seed oblong-obovate, amphitropous, with prominent rounded operculum.—Stagnant waters, throughout N. Am. (Eu.)
[*][*] Ovules 2–7, anatropous; fronds very thick and spongy, flat above, very obscurely 5-nerved (1½–3´´ long).