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FNA | Family List | FNA Vol. 22 | Lemnaceae

2. Lemna Linnaeus, Sp. Pl. 2: 970. 1753; Gen. Pl. ed. 5; 417, 1754.

Duckweed, lenticules [Greek name of a water plant]

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..

Species 13 (9 in the flora): worldwide except arctic and antarctic regions.

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).

1 Fronds submersed (except when flowering or fruiting), margins denticulate distally, 2--3.5 times as long as wide, base suddenly narrowed into green stalk, 2--20 mm.   5 Lemna trisulca
+ Fronds floating, margins entire, 1--3 times as long as wide.   (2)
2 (1) Fronds with 1 vein.   (3)
+ Fronds with 3--5(--7) veins.   (4)
3 (2) Vein mostly prominent, longer than extension of air spaces, or running through at least 3/4 distance between node and apex   8 Lemna valdiviana
+ Vein sometimes indistinct, very rarely longer than extension of air spaces, not longer than 2/3 distance between node and apex   9 Lemna minuta
4 (2) Root sheath winged at base; root tip usually sharp pointed; roots to 3(--3.5) cm; fronds without reddish color or spots of anthocyanin, mostly with 1 very distinct papilla near apex on upper surface.   (5)
+ Root sheath not winged; root tip mostly rounded; roots often longer than 3 cm; fronds often with reddish tinge or spots of anthocyanin, with or without distinct papilla near apex on upper surface.   (6)
5 (4) Seeds with 35--70 indistinct ribs (to count ribs remove membranous pericarp), staying within fruit wall after ripening; root sheath wing 2--3 times as long as wide   6 Lemna perpusilla
+ Seeds with 8--26 distinct ribs, falling out of fruit wall after ripening; root sheath wing 1--2.5 times as long as wide   7 Lemna aequinoctialis
6 (4) Plants forming small, olive to brown, rootless turions, which sink to bottom   4 Lemna turionifera
+ Plants usually without distinct turions.   (7)
7 (6) Largest air spaces longer than 0.3 mm; if red-colored on lower surface, coloring beginning from margin; ovary (1--)2--7-ovulate   1 Lemna gibba
+ Largest air spaces 0.3 mm or shorter; if pigmented on lower surface, red coloring beginning from attachment point of root; ovary 1-ovulate.   (8)
8 (7) Fronds not reddish on lower surface (or at least much less so than on upper); greatest distance between lateral veins near or proximal to middle.   3 Lemna minor
+ Fronds often reddish on lower surface (more intensely so than on upper); greatest distance between lateral veins near or distal to middle.   (9)
9 (8) Fronds flat, with mostly distinct papillae on midline of upper surface; seeds with 30--60 indistinct ribs   4 Lemna turionifera
+ Fronds often gibbous, with very distinct papillae above node and near apex on upper surface but not between node and apex; seeds with 10--16 distinct ribs KSN:>2. Lemna obscura   (1)

Lower Taxa


Related Objects  

Flora of China  
  • Lemna (PDF)
  • PDF
    Photos by The Biodiversity of the Hengduan Mountains Project  
  • Image File (David Boufford)
  • Image/JPEG
  • Image File (David Boufford)
  • Image/JPEG

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