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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

LEMNA DUCKWEED

Wayne P. Armstrong


Plants much reduced, not differentiated into stems, leaves; floating aquatic; root generally 1, generally 2–6 mm, sheath near base generally not winged. Plant body: generally in 2s to 8s; generally 2–5 mm, flat, generally widely elliptic to oblong, pale to dark green, often ± red; veins 1–5; winter buds generally 0. Inflorescence: flowers in 2 lateral pouches, sheathed by minute membrane. Fruit: generally unwinged. Seed: ribbed, generally smooth between ribs.
14 species: worldwide. (Greek: lake or swamp) Lemna obscura (Austin) Daubs. [Lemna minor L. var. obscura Austin] excluded.

Key to Lemna

1. Plant body 6–10 mm, on tapered stalk, often in branched chains of 8–30 ..... L. trisulca

1' Plant body 1–6 mm, appearing sessile, single or generally in 2s to 8s

2. Veins per plant body 1 (sometimes obscure)

3. Plant body 1–2.5 mm, generally thinner at margin, generally in 2s, not attached; vein < 2/3 distance from root attachment to tip of plant body ..... L. minuta

3' Plant body 2–4 mm, thin ± throughout, often in 4s to 8s, attached; vein up to 3/4 distance from root attachment to tip of plant body ..... L. valdiviana

2' Veins per plant body 3–5

4. Root sheath with 2 obvious, wing-like appendages at base ..... L. aequinoctialis

4' Root sheath not winged

5. Plant body widely elliptic to round, tip asymmetric, lower surface generally convex ..... L. gibba

5' Plant body widely elliptic to obovate, tip generally symmetric, lower surface flat

6. Upper surface generally smooth; lower surface green; winter buds 0 ..... L. minor

6' Upper surface midline generally with row of minute bumps; lower surface often ± red in age; winter buds dark green or brown in fall ..... L. turionifera

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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