Potamogeton gramineus |
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grass-leaf pondweed, grassy pondweed, potamot à feuilles de graminées, variable pondweed, variable-leaf pondweed |
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Rhizomes | present. |
Cauline stems | terete to flattened, without spots, to 150 cm; nodal glands absent. |
Turions | absent. |
Leaves | both submersed and floating or submersed only, ± spirally arranged. |
Floating leaves | petioles continuous in color to apex, 3–4.5 cm; blade yellow-green to dark green, elliptic to ovate, 3.5–4 cm × 16–20 mm, base rounded, apex acuminate; veins 11–13. |
Submersed leaves | sessile or rarely petiolate, lax; stipules persistent, inconspicuous, convolute, free from blade, pale green to brown, not ligulate, 1.3–1.6 cm, not fibrous, not shredding at tip, apex acute to obtuse; petioles to 3 cm; blade light green to brownish green, elliptic, not arcuate, 3.1–9.1 cm × 3–27 mm, base attenuate, without basal lobes, not clasping, margins entire, rarely crispate, apex not hoodlike, acuminate, lacunae in 1–2 rows each side of midvein; veins 3–9. |
Inflorescences | emersed, unbranched; peduncles not dimorphic, both axillary and terminal, erect to ascending, cylindric, 3.2–7.7 cm; spikes not dimorphic, cylindric, 15–35 mm. |
Fruits | sessile, greenish brown, ovoid, laterally compressed, abaxially and laterally keeled, 1.9–2.3 × 1.8–2 mm, lateral keels without points; beak erect, 0.3–0.5 mm; sides without basal tubercles; embryo with less than 1 full spiral. |
2n | = 52. |
Potamogeton gramineus |
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Phenology | Flowering summer–fall. |
Habitat | Ponds, lakes, streams, and rivers |
Elevation | 0–3500 m (0–11500 ft) |
Distribution |
AK; AZ; CA; CO; CT; IA; ID; IL; IN; KS; KY; MA; MD; ME; MI; MN; MT; ND; NE; NH; NJ; NV; NY; OH; OR; PA; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; SPM; Greenland; Eurasia
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Discussion | Seven hybrids, Potamogeton gramineus × P. nodosus (= P. × argutulus Hagström), P. gramineus × P. richardsonii (= P. hagstroemii A. Bennett [as hagstromii]), P. alpinus × P. gramineus (= P. × nericius Hagström), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), P. gramineus × P. natans (= P. × sparganiifolius Laestadius ex Fries), P. gramineus × P. illinoensis [= P. × spathuliformis (J. W. Robbins) Morong)], and P. gramineus × P. praelongus (= P. × vilnensis Galinis), have been described. Three varieties were recognized (E. C. Ogden 19435) and treated (M. L. Fernald 1950). These varieties, Potamogeton gramineus var. gramineus, deletion}P. gramineus var. myriophyllus, and P. gramineus var. maximus, were said to be separated by the shape and size of the submersed leaves. We have studied many populations of this species in the field and have observed on several occasions that a single population has leaf morphology variable enough to include all three varieties. We have, , therefore, chosen not to recognize any infraspecific categories for this species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton |
Sibling taxa | |
Synonyms | P. gramineus var. maximus, P. gramineus var. myriophyllus |
Name authority | Linnaeus: Sp. Pl. 1: 127. 1753 (as gramineum) |
Web links |
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