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Published In: Species Plantarum 2: 970. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/22/2009)

 

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1. Lemna L. (duckweed)

Plants of 1–3 unequal, connected fronds, or in L. trisulca of up to 50 fronds in an irregular mass. Roots 1 per frond, attached at a node near the frond base. Fronds flattened or gibbous (strongly convex) beneath, ovate to obovate or oblong, in L. trisulca with a persistent stalklike base, green or sometimes with reddish margins, spots, or areas, the upper surface sometimes with a row of papules along the midvein. Veins 1–5. Pouches 2, along the margin near node. Fruits lacking wings or with narrow, lateral wings. Thirteen species, worldwide.

 

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1 Plants usually submerged; up to 50 fronds connected by narrowed, stalklike bases, forming dense clusters, the frond margins toothed or irregular 6 Lemna trisulca
+ Plants usually floating or forming mats on mud at water’s edge; fronds single or 2 or 3 connected by small stalks that soon wither, the bases rounded, the margins entire (2)
2 (1) Fronds with 1 vein (3)
+ Fronds with 3–5 veins; species very difficult to distinguish vegetatively (4)
3 (2) Fronds mostly 1–3 mm long, usually symmetrical (right side of surface similar in shape to the left); vein usually indistinct, extending less than 2/3 of the distance from the attachment point of the roots to the tip 3 Lemna minuta
+ Fronds mostly 2.5–5.0 mm long, usually asymmetrical (right and left sides different in shape); vein usually distinct, extending more than 3/4 of the distance from the attachment point of the roots to the tip 8 Lemna valdiviana
4 (2) Roots less than 3 cm long, sharply pointed at the tip when fresh, the sheath at the base with a narrow, transparent wing (visible when fresh under magnification); fronds without reddish areas or spots (5)
+ Roots sometimes more than 3 cm long, blunt at the tip when fresh, the bases not winged; fronds often with reddish margins, spots, or areas (6)
5 (4) Seeds with 35–70 indistinct ribs; fronds usually with the largest 2 or 3 papules near the node 5 Lemna perpusilla
+ Seeds with 8–26 strong ribs; fronds usually with the largest papule near the edge 1 Lemna aequinoctialis
6 (4) Seeds with 30–60 indistinct ribs; fronds 1.5–4.0 mm long, with line of quite distinct papules when fresh, the ones nearest the apex not larger than the rest; plants producing rounded, rootless, olive to brown turions (specialized overwintering structures) late in year 7 Lemna turionifera
+ Seeds with 10–16 strong ribs; fronds 1–8 mm long, with line of relatively indistinct, small papules or the papule nearest the apex much larger than the rest; plants not producing turions (7)
7 (6) Fronds 2–8 mm long, nearly flat on both surfaces, the papules all relatively small 2 Lemna minor
+ Fronds 1.0–3.5 mm long, the lower surface usually gibbous (strongly convex), the papule nearest the apex much larger than the rest 4 Lemna obscura
 
 
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