Potamogeton alpinus |
Potamogeton pusillus subsp. tenuissimus(synonym of Potamogeton berchtoldii) |
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alpine pondweed, northern pondweed, potamot alpin, reddish pondweed |
Berchtold's pondweed, narrow leaf pondweed |
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Cauline stems | terete, without spots, to 200 cm; nodal glands absent. |
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Turions | absent. |
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Leaves | submersed and floating or floating absent, ± spirally arranged. |
stipules convolute; blade 0.9–5.4 cm × 0.2–2.5 mm; apex acute to obtuse, lacunae in 1–5 rows each side of midrib; veins 1–3(–5). |
Floating leaves | petioles continuous in color to apex, 0.1–1.2 cm; blade reddish green, elliptic or oblanceolate to obovate or oblong-linear, 4–7(–10) cm × 10–25(–40) mm, base gradually tapering into petiole, apex obtuse or acute; veins (7–)9–13(–15). |
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Submersed leaves | sessile, lax; stipules persistent, inconspicuous, convolute, free from blade, light brown to reddish, not ligulate, (1.2–)1.5–2.5(–4) cm, not fibrous, not shredding at tip, apex blunt; blade reddish green, oblong-linear to linear-lanceolate, not arcuate, 4.5–18(–25) cm × 5–20 mm, base rounded, without basal lobes, slightly clasping, margins entire, not crispate, apex not hoodlike, obtuse or acute, lacunae in 0–6 rows each side of midvein; veins 7–9. |
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Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect, cylindric, 3–10(–16) cm; spikes not dimorphic, cylindric, 10–35 mm. |
peduncles more than 3 per plant, cylindric to slightly clavate; spikes capitate to cylindric, continuous. |
Fruits | pedicellate, tawny olive-green, obovoid, plump, turgid, abaxially keeled, laterally keeled or not, (2.5–)3–3.5 × (1.7–)2–2.4 mm, lateral keels when present without points; beak abaxially curved, 0.5–0.9 mm; sides without basal tubercles; embryo with 1 full spiral. |
ovoid, sides rounded, rarely concave; beak median, rarely toward adaxial edge. |
Rhizome | present. |
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2n | = 52. |
= 26. |
Potamogeton alpinus |
Potamogeton pusillus subsp. tenuissimus |
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Phenology | Flowering early summer–fall. | Flowering and fruiting summer–fall. |
Habitat | Ponds, lakes, and slow-moving streams | Shallow waters of lakes and streams |
Elevation | 400–2500 m (1300–8200 ft) | 0–2100 m (0–6900 ft) |
Distribution |
AK; CA; CO; ID; MA; ME; MI; MN; MT; NH; NJ; NV; NY; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Greenland; Europe; Asia Eurasia
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AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KY; LA; MA; MD; ME; MI; MN; MS; MT; NC; ND; NH; NJ; NV; NY; OH; OK; OR; PA; RI; SC; VA; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Eurasia |
Discussion | Plants of Potamogeton alpinus often are red whenever taken from the water, a feature that makes this species quite distinctive. Two varieties, Potamogeton alpinus var. tenuifolius and var. subellipticus, have been recognized in North America, based mainly on submersed leaf shape. Plants bearing both leaf types have been observed in the same population; hence the varieties are not recognized. Four hybrids, Potamogeton alpinus × P. nodosus (= P. ×subobtusus Hagström), P. alpinus × P. gramineus (= P. xnericius Hagström), P. alpinus × P. praelongus (= P. ×griffithii A. Bennett), and P. alpinus × P. perfoliatus (= P. ×prussicus Hagström), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Although Delaware and West Virginia lies within the mapped area, we know of no collections from that state. Potamogeton pusillus subsp. tenuissimus is the most common linear-leaved subspecies of the family in temperate North America. Whenever one finds a linear-leaved pondweed with 1–5 rows of lacunae on each side of the midvein, chances are that it is subsp. tenuissimus. Only Potamogeton obtusifolius could be confused with the taxon, and it can be separated by having its cylindric inflorescence, whereas subsp. tenuissimus has a capitate inflorescence. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton > Potamogeton pusillus |
Sibling taxa | ||
Synonyms | P. alpinus subsp. tenuifolius, P. alpinus var. subellipticus, P. alpinus var. tenuifolius, P. tenuifolius, P. tenuifolius var. subellipticus | P. pusillus var. tenuissimus, P. berchtoldii, P. berchtoldii var. colpophilus, P. berchtoldii var. lacunatus, P. berchtoldii var. polyphyllus, P. berchtoldii var. tenuissimus |
Name authority | Balbis: Misc. Bot. 13. (1804) | (Mertens & W. D. J. Koch) R. R. Haynes & Hellquist: Novon 6: 370. (1996) |
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