Potamogeton gramineus L.

  • Authority

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

  • Family


  • Scientific Name

    Potamogeton gramineus L.

  • Type

    Type. Europe. Lapland, 1732, C. Linnaeus s.n. (lectotype, designated by Haynes, 1986, Institute de France).

  • Description

    Species Description - Rhizomes present; erect stems terete to flattened, without spots, to 150 cm long. Leaves both submersed and floating or submersed only, ± spirally arranged; submersed leaves sessile or rarely petiolate, lax, entire to crisped, light green to brownish green, the blades elliptic, 3-9-veined, 3.1-9.1 x 0.3-2.7 cm, with 1-2 rows of lacunae each side of midvein, the apex noncucullate, acuminate, the base attenuate, without basal lobes, the glands absent, the petiole to 3 cm long, the ligules inconspicuous, acute, free from blade, nonligulate, nonfibrous, not shredding at tip, 1.3-1.6 cm long, apex obtuse; floating leaves petiolate, yellow-green to dark green, the blades elliptic to ovate, 11-13-veined, 3.5-4 x 1.6-2 cm, the apex acuminate, the base rounded, the petiole continuous in color to apex, 3-4.5 cm long. Turions absent. Inflorescences unbranched; peduncles similar, cylindric, both axillary and terminal, erect to ascending, 3.2-7.7 cm long; spikes similar, cylindric, 1.5-3.5 cm long. Fruits sessile, ovate, laterally compressed, greenish brown, with well-developed abaxial keel and lateral keels, 1.9-2.3 x 1.8-2 mm, lateral keels without points; beak erect, 0.3-0.5 mm long; sides without basal tubercles; embryo with less than one full spiral.

  • Discussion

    Potamogeton gramineus has not been considered to be part of the flora of the Bahama archipelago, and it was not included by Correll and Correll (1982), who instead determined everything similar to P. gramineus from the Bahamas as P. illinoensis Morong. We have examined nearly two dozen collections of the P. gramineus/P. illinoensis complex collected in the Bahama archipelago. All but two of those collections exactly matched P. gramineus from the north temperate areas. We were presented with a problem of how to interpret the complex in the Bahamas. Either we would accept a third species in the complex that was known from the Bahamas alone, combine the two species into one, or accept P. gramineus as part of the Bahama archipelago flora. We have chosen the third option because one of us (Haynes) knows many localities in North America where the two taxa occur in the same body of water (oftentimes nearly adjacent to one another), and because it would be nearly impossible to compile a description to separate the Bahama collections from the north temperate collections.

  • Distribution

    Temperate North America, Europe, and Asia. Fresh waters of ponds, lakes, streams, and rivers, at elevations from near sea level to 2500 m.

    Bahamas South America| Acklins Bahamas South America| Andros Island Bahamas South America| South Andros Bahamas South America| Cat Island Bahamas South America| Great Abaco Bahamas South America| Exuma Bahamas South America| New Providence Bahamas South America| New Providence Bahamas South America| Eleuthera Bahamas South America| San Salvador Bahamas South America| North Andros Bahamas South America| Inagua Bahamas South America|