Potamogeton

• Authority

  Haynes, Robert R. & Holm-Nielsen, Lauritz B. 2003. Potamogetonaceae. Fl. Neotrop. Monogr. 85: 1-52. (Published by NYBG Press)

• Family

  Potamogetonaceae

• Scientific Name

  Potamogeton

• Description

  
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  Genus Description - Herbs propagated by seeds, turions, or rhizomes; stems terete or compressed, the nodes occasionally with oil glands. Leaves submersed or both submersed and floating, alternate to subopposite; submersed leaves pellucid, sessile or petiolate, linear to orbicular, noncaniculate, flattened, subulate to obtuse at apex, acute to perfoliate at base, the margins entire or serrate, rarely crimped, the veins 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 entire, the veins 1-51; basal sheaths tubular, sheathing stem and young inflorescences, connate or convolute, either free from or adnate to base of submersed leaves for less than 1/2 the length of basal sheaths, free from base of floating leaves. Turions present or absent, with extremely shortened internodes, divided into inner and outer leaves, the inner leaves few to numerous, rolled into a fusiform structure, unmodified, or shortened and oriented at 90° angles with respect to outer leaves, the outer leaves 1-5 per side, mostly similar to vegetative leaves or occasionally corrugated near the base. Inflorescence a capitate or cylindrical spike or panicle of spikes with 1-20 whorls of flowers, compact or moniliform, with 2-4 flowers in each whorl, submersed or held above surface of water; peduncle stiff, if long enough, projecting the inflorescence above water surface. Flowers with perianth of 4, free, rounded, short-clawed segments; androecium of 4 stamens, filaments adnate to the perianth claw; anthers 2-locular; gynoecium of 1 or 4 carpels. Fruits abaxially rounded or keeled, beaked; embryo coiled 1 or more times. Chromosomes: x = 13 or 14.

• Discussion

  [Greek potamos, river, geiton, neighbor]

• Distribution

  A near cosmopolitan genus of ca. 95 species; 17 species are known from the Neotropics and temperate South America. González (1989) lists an additional species, Potamogetón natans, but we are not including it here since the species is included in numerous treatments of the genus for North America.