Potamogeton groenlandicus |
Potamogeton richardsonii |
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Greenland pondweed |
clasping-leaf pondweed, potamot de Richardson, Richardson's pondweed |
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Cauline stems | terete, without spots, 20–50 cm; glands white, 0.1–0.7 mm diam. |
terete, without spots, to 100 cm; nodal glands absent. |
Turions | terminal or axillary, common, 4.2–8.4 cm × 1.4–2.5 mm, soft; leaves ± 4-ranked; outer leaves 2 per side, base without corrugations, apex acute to apiculate; inner leaves unmodified. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, delicate; stipules deliquescent to persistent, inconspicuous, convolute, free from blade, brown, not ligulate, 0.45–1.91 cm, not fibrous, not shredding at tip, apex obtuse; blade pale to deep green, linear, not arcuate, 2.6–8.8 cm × 0.7–1.7 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or present, 0–3 rows each side of midrib; veins 7–11. |
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. |
Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal, erect, cylindric, 20 mm; spikes not dimorphic, cylindric, 5 mm. |
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. |
Fruits | not laterally keeled, 2.6–2.7 × 2 mm; beak erect, 0.3 mm; sides without basal tubercles; embryo with 1 full coil. |
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. |
Rhizome(s) | absent. |
present. |
2n | = 26. |
= 52. |
Potamogeton groenlandicus |
Potamogeton richardsonii |
|
Phenology | Flowering late summer. | Flowering summer–fall. |
Habitat | Ponds and lakes | Alkaline waters of lakes, streams, and rivers |
Elevation | 10–450 m (0–1500 ft) | 0–3000 m (0–9800 ft) |
Distribution |
Greenland |
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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Discussion | Of conservation concern. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | P. pusillus subsp. groenlandicus | P. perfoliatus var. richardsonii, P. perfoliatus subsp. richardsonii |
Name authority | Hagström: Kongl. Svenska Vetenskapsakademiens Handlingar n.s. 55(5): 127. (1916) | (A. Bennett) Rydberg: Bulletin of the Torrey Botanical Club 32: 599. (1905) |
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