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(Last Modified On 10/31/2012)
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(Last Modified On 10/31/2012)
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Family
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LEMNACEAE
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Description
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Plants very small or minute, oval, globular, or ensiform fronds (modified stems) free or variously attached, floating upon or beneath the surface of pools or sluggish streams, occasionally deposited on mud or wet rocks bordering a body of water. Roots present or absent.! Inflorescence an extremely reduced spadix consisting of 1 pistillate and 1-2 staminate flowers, the whole immersed within a small pouch in the upper surface of the frond, naked or surrounded by an inconspicuous, vaginate spathe. Pistillate flowers naked, consisting of a single pistil containing 1 to several ovules. Staminate flowers naked, consisting of a single stamen.
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Note
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The Lemnaceae include the Duck-weeds of the United States. They frequently occur in such great numbers that the whole surface of a pond may appear green, as though covered by a "water-bloom" of algae. For the determination of the Panamanian specimens cited in this account, the authors are indebted to Dr. W. H. Camp of the New York Botanical Garden. The text of the account is drawn largely from the works of C. H. Thompson (Ann. Rept. Missouri Bot. Gard. 7:101-111, pI. 64-66. 1896; ibid., 9:21-42, pI. I-4. 1898 [reprint, pp. 1-22. 1897] ).
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Key
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a. Fronds with solitary roots and 2 reproductive pouches -1. LEMNA aa. Fronds without roots and with 1 reproductive pouch. b. Fronds thin, ligulate - --2. WOLFFIELLA bb. Fronds thick, globular --- --3. WOLFFIA
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