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(Last Modified On 5/24/2013)
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(Last Modified On 5/24/2013)
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Genus
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Potamogeton L.
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PlaceOfPublication
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Sp. P1. 126. 1753.
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Synonym
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Hydrogeton Lour., Fl. Cochinchinensis 244. 1790. Patamogeton Honckery, Syn. Plan. Germ. 2: 110. 1793. Potamogiton Raf., Med. Respos. 5: 354. 1808. Potamogetum Clairville, Man. Herb. Suisse & Valais 34. 1811. Peltopsis Raf., Jour. Phys. Chim. Hist. Nat. Arts 89: 102. 1819. Spirillus J. Gay, Compt. Rend. Hebd. Seances Acad. Sci. 38: 703. 1854.
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Description
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Plants annual or perennial, propagated from seeds, winter buds, or rhizomes, submersed in fresh or rarely brackish water. Stems variable in length according to water depth, branched or unbranched, terete or compressed, rooting at the nodes. Leaves all submersed and/or floating, alternate or subopposite; submersed leaves pellucid, sessile or petiolate, linear to orbicular, apically subulate to ob- tuse, basally cuneate to rounded or cordate, the margins entire, the nerves 1-35; floating leaves coriaceous, mostly petiolate, rarely subsessile, elliptic to ovate, acute to obtuse at apex, cuneate to rounded or cordate at base, the margins en- tire, the nerves 3-51; stipules tubular, sheathing the stem and young inflores- cences, connate or convolute, either free or adnate to the base of submersed leaves, free from the base of floating leaves. Winter buds present or absent, with extremely shortened internodes, divided into inner and outer leaves; inner leaves few to numerous, unmodified or shortened and oriented at 90? with respect to outer leaves, rolled into a fusiform structure; outer leaves 1-5 per side, mostly similar to vegetative leaves, rarely corrugated near the base. Inflorescence a capitate or cylindric spike with 1-20 whorls of flowers, compact or moniliform, with 2-4 flowers in each whorl, mostly buoyed above surface of water at an- thesis. Flowers bisporangiate; perianth of 4 distinct, rounded, short-clawed, greenish segments; stamens 4, the filaments adnate to the perianth claw, the anthers bithecate, extrorse, pollen spherical, monoaperturate; gynoecium of 4 distinct, unilocular, uniovulate carpels, the placentation parietal, the ovule campylotropus. Fruit drupe-like, dorsally rounded or keeled; embryo coiled.
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Distribution
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A genus of perhaps 100 species, widespread throughout both hemispheres, especially in temperate and subtemperate regions.
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Note
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One species, Potamogeton illinoensis, is known to occur in Panama. Other species, e.g. P. foliosus and P. pusillus, occur north and south of Panama and may be found in the country. Species of Potamogeton, commonly known as "pondweed," are one of the most important food sources of waterfowl and other vertebrates. The plants also pro- vide cover and breeding areas for many fishes and invertebrates. In some areas, pondweeds occur in such abundance that they are considered troublesome weeds.
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Reference
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Fernald, M. L. The linear-leaved North American species of Potamogeton section Axillares. Mem. Amer. Acad. Arts 17: 1-183. 1932. (Also, Mem. Gray Herb. 3.) Haynes, R. R. A revision of North American Potamogeton subsection Pusilli (Potamogetonaceae). Ph.D. Dissertation, Ohio State University. 140 p. 1973.
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Reference
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Ogden, E. C. The broad-leaved species of Potamogeton of North America north of Mexico. Rhodora 45: 57-105, 119-163, 171-214. 1943.
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