Potamogeton pusillus L.
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Authority
Haynes, Robert R. & Holm-Nielsen, Lauritz B. 2003. Potamogetonaceae. Fl. Neotrop. Monogr. 85: 1-52. (Published by NYBG Press)
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Family
Potamogetonaceae
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Scientific Name
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Description
Species Description - Rhizomes absent; erect stems terete to slightly compressed, without spots, 18-150 cm long. Leaves submersed, sessile, ± spirally arranged, delicate to coarse, entire, noncrisped, pale green to olive, rarely rufescent, linear, nonarcuate, l-3(-5)-veined, 0.9-6.5 x 0.2-2.5 mm, lacunae absent or to 5 rows each side of midrib, the apex noncucullate, subulate to obtuse, the base without basal lobes; glands present or absent, green, gold, brown, or rarely white, to 0.5 mm diam.; ligules inconspicuous, free from base of blade, nonligulate, brown to green or white, rarely appearing fibrous, not shredding at tip, connate or convolute, 3.1-9.2 mm long, the apex obtuse. Turions common, soft, lateral or terminal, 0.9-3.2 cm x 0.3-1.8 mm; inner leaves rolled into a hardened fusiform structure; outer leaves 1-3 per side, subulate or obtuse, without corrugations at base. Inflorescences unbranched; peduncles all similar, filiform to slightly clavate, axillary or terminal, mostly erect, rarely recurved, 0.5-6.2(-6.6) cm long; spikes all similar, capitate to cylindric, 1.5-10.1 mm long. Fruits sessile, ovate to obovate, turgid to compressed, green to brown, without abaxial or lateral keels, 1.5-2.2 x 1.2-1.6 mm; beak erect, 0.1-0.6 mm long; sides without basal tubercles; embryo with less than one full spiral.
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Discussion
The species has been divided into three subspecies (see Haynes & Hellquist, 1996). Only one subspecies is known from the Neotropics.