Roots 1 per frond. Fronds floating or submersed, 1 or 2--20 or more, coherent in groups or forming chains, lanceolate-ovate, flat or gibbous, 1--15 mm, margins entire or denticulate, upper surfaces sometimes with small conic papillae along veins (especially at node and near apex); air spaces in tissue; reproductive pouches 2, lateral, at base from which daughter fronds and flowers originate, triangular; veins 1--5(--7), originating from point in proximal part of frond (node) or if more than 3 veins present, outer ones sometimes branching distally from inner ones; scale at base of frond absent; anthocyanins sometimes present; pigment cells absent (red pigmentation present in some species); turions absent (sometimes present in L. turionifera). Flowers 1(--2) per frond, surrounded by small utricular, membranous scale; stamens 2, 4-locular. Seeds 1--5, longitudinally ribbed. x = 10, 21, 22.. In Lemna the connection to the mother frond is formed by a thin white stipe at the base that falls off or decays after the frond is grown (frond of L. trisulca is narrowed at base into a green stalk persisting on frond).
FRONDS: floating on or below the surface of the water, lanceolate to ovate, with entire or denticulate margins, flat or gibbous, with air spaces in tissue, with two triangular lateral reproductive pouches at the base from which daughter fronds and flowers originate, without a scale at the base; nerves 1 5( 7); root 1; anthocyanins sometimes present; pigment cells absent. FLOWERS: 1( 2) per frond, surrounded by a scale; stamens 2, 4 locular. SEEDS: 1 5, longitudinally ribbed. NOTES: l3 spp.; worldwide (except arctic and antarctic zones). (Greek name of a water plant). REFERENCES: Landolt, Elias. 1992. Lemnaceae. Ariz.-Nev. Acad. Sci. 26(1)2.
Thallus flat to strongly convex beneath, variously rotund, ovate, obovate, oblong, or stipitate, with 1-5 obscure nerves from a nodal point near the base, or nerveless; root 1, opposite the nodal point, without vascular tissue, surrounded by an inconspicuous short sheath at base; reproduction as in Spirodela; ovules 1-6; seed longitudinally ribbed and transversely striate, or smooth. 10, cosmop.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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