Potamogeton richardsonii |
Potamogeton perfoliatus |
|
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clasping-leaf pondweed, potamot de Richardson, Richardson's pondweed |
clasping-leaf pondweed, potamot perfolié |
|
Cauline stems | terete, without spots, to 100 cm; nodal glands absent. |
terete, without spots, to 250 cm; nodal glands absent. |
Turions | absent. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, lax; stipules persistent, conspicuous, convolute, free from blade, white, not ligulate, 0.12–0.17 cm, fibrous, disintegrating to persistent fibers, even on proximal portion of stem, shredding at apex, apex obtuse; blade olive green, ovate-lanceolate to narrowly lanceolate, not arcuate, 1.6–13 cm × 5–28 mm, base rounded, without basal lobes, clasping, margins entire to crispate, apex not hoodlike, not splitting when pressed, acute to obtuse, lacunae absent; veins 3–35. |
submersed, ± spirally arranged, sessile, lax; stipules deteriorating into fibers and deciduous, inconspicuous (absent on proximal portion of stem), convolute, free from blade, light brown to green, not ligulate, 3.5–6.5 cm, not fibrous, not shredding at apex; blade olive-green, broadly lanceolate, orbiculate, or ovate, not arcuate, 0.9–7.6(–9.7) cm × 7–40 mm, base rounded, without basal lobes, clasping, margins entire, often crispate, apex not hoodlike, not splitting when pressed, round, rarely acute; veins 3–25. |
Inflorescences | emersed, unbranched; peduncles not dimorphic, terminal or axillary, erect to rarely recurved, clavate, 1.5–14.8 cm; spikes not dimorphic, cylindric, 13–37 mm. |
unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect to rarely recurved, cylindric, 1–7.3 cm; spike not dimorphic, cylindric, 0.4–4.8 cm. |
Fruits | sessile, greenish brown, obovoid, turgid to concave, not or rarely abaxially keeled, not laterally keeled, 2.2–4.2 × 1.7–2.9 mm; beak erect, 0.4–0.7 mm; sides without basal tubercles; embryo with 1 full spiral. |
sessile, greenish brown to olive-green, obovoid, turgid or rarely concave, not abaxially or laterally keeled, 1.6–3 × 1.3–2.2 mm; beak erect, 0.4–0.6 mm; sides without basal tubercles; embryo with 1 full spiral. |
Rhizome(s) | present. |
present. |
2n | = 52. |
= 52. |
Potamogeton richardsonii |
Potamogeton perfoliatus |
|
Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Alkaline waters of lakes, streams, and rivers | Waters, often brackish, of lakes, streams, rivers, and bays |
Elevation | 0–3000 m (0–9800 ft) | 0–100 m (0–300 ft) |
Distribution |
AK; CA; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NS; NT; ON; QC; SK; YT
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AL; CT; DC; DE; FL; LA; MA; MD; ME; NC; NH; NJ; NY; OH; PA; RI; VA; VT; NB; NL; NS; ON; PE; QC; SPM; Africa; Greenland; Eurasia; Central America (Guatemala); Australia
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Discussion | Potamogeton richardsonii is quite similar to P. perfoliatus. Specific characteristics to separate the two species are the shape of the leaf blade apex, acute in P. richardsonii and obtuse in P. perfoliatus, and the condition of the stipules, disintegrating between the veins leaving fibrous strands in P. richardsonii, and the entire stipule, including the veins, disintegrating in P. perfoliatus. Two hybrids, Potamogeton gramineus × P. richardsonii (= P. × hagstroemii A. Bennett [as hagstromii]) and P. nodosus × P. richardsonii (= P. × rectifolius A. Bennett), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. perfoliatus × P. pusillus (= P. × mysticus Morong), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), and P. alpinus × P. perfoliatus (= P. × prussicus Hagström), have been described. (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. perfoliatus var. richardsonii, P. perfoliatus subsp. richardsonii | |
Name authority | (A. Bennett) Rydberg: Bulletin of the Torrey Botanical Club 32: 599. (1905) | Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) |
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