Flora of Oregon

Plants free-floating aquatics, floating on the surface or submersed; small, green, sometimes reddish, flat plant bodies without true stems and leaves; veins 1–5 per plant body.

Roots (0)1.

Buds formed in 2 lateral pouches; turions present in some species.

Inflorescences a single flower in a membranous spathe within the budding pouch, rarely produced.

Flowers bisexual; tepals 0; stamens 2.

Fruits 1–several seeded follicles.

Cosmopolitan. 13 species; 6 species treated in Flora.

Lemna rarely flower, but reproduction by budding is common. Daughter plants usually appear sessile but are connected to the mother plant by a short, thin, white stipe that decays after the daughter plant is grown. The exception is Lemna trisulca, in which the stipe is long and green and usually remains connected, resulting in a network of plant bodies. Vein morphology is best determined on fresh material using backlighting.

Flora of North America

as described under Lemna

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).