Potamogeton diversifolius |
Potamogeton gramineus |
|
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diverse-leaf pondweed, Rafinesque's pondweed, water-thread pondweed |
grass-leaf pondweed, grassy pondweed, potamot à feuilles de graminées, variable pondweed, variable-leaf pondweed |
|
Rhizomes | present. |
present. |
Cauline stems | compressed, without spots, 10–35 cm; glands absent. |
terete to flattened, without spots, to 150 cm; nodal glands absent. |
Turions | absent. |
absent. |
Leaves | both submersed and floating or floating absent, ± spirally arranged. |
both submersed and floating or submersed only, ± spirally arranged. |
Floating leaves | petiolate; petioles continuous in color to apex, 0.7–0.8 cm; blade adaxially light green, obovate to elliptic, 0.8–1.6 cm × 3–8.5 mm, base acute, apex round to acute; veins 3–7. |
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, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade ½ stipule length, light brown to red-brown, ligulate, 1.5–2.3 cm, not fibrous, not shredding at tip, apex obtuse; blade red-brown to light green, linear, often arcuate, 1–1.3 cm × 0.1 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae present, 1–2 rows each side midrib; veins 1. |
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 | unbranched; peduncles dimorphic, submersed axillary, recurved, clavate, 3–5 mm, emersed axillary or terminal, erect to slightly recurved, clavate, 6–15 mm; spikes dimorphic, submersed capitate, 2–3 mm, emersed cylindric, 5–9.7 mm. |
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, orbicular, compressed, abaxially winged, laterally winged, 1–1.5 × 0.9–2 mm, lateral wings with sharp points; beak present, erect, 0.1 mm; sides without basal tubercles; embryo with more than 1 full spiral. |
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. |
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Potamogeton diversifolius |
Potamogeton gramineus |
|
Phenology | Flowering and fruiting spring–fall. | Flowering summer–fall. |
Habitat | Ponds, lakes, streams, and rivers | Ponds, lakes, streams, and rivers |
Elevation | 5–2500 m (0–8200 ft) | 0–3500 m (0–11500 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; MN; MO; MS; MT; NC; ND; NE; NJ; NV; NY; OH; OK; OR; PA; SC; SD; TN; TX; VA; VT; WI; WV; Mexico; Wyo
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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 | Potamogeton diversfolius is very likely the most common species of Potamogeton the genus in the southeastern United States. It has been separated into two species, P. diversifolius in the strict sense and P. capillaceus (M. L. Fernald 1932). The species has also been divided into two varieties, var. diversifolius and var. trichophyllous Morong (D. O S. Correll and M. C. Johnston 1970) . Potamogeton diversifolius var. trichophyllous actually is misapplied, as the name really refers to the more northern P. bicupulatus Fernald. We are following E. J. Klekowski Jr. and E. O. Beal (1965) in accepting only one taxon, as we have studied the species over much of its range and reached similar conclusions. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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. | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton |
Sibling taxa | ||
Synonyms | P. capillaceus | P. gramineus var. maximus, P. gramineus var. myriophyllus |
Name authority | Rafinesque: Medical Repository hexade 2, 5:354. (1808) | Linnaeus: Sp. Pl. 1: 127. 1753 (as gramineum) |
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