Potamogeton obtusifolius |
Potamogeton alpinus |
|
---|---|---|
blunt-leaf pondweed, potamot à feuilles obtuses |
alpine pondweed, northern pondweed, potamot alpin, reddish pondweed |
|
Cauline stems | slightly compressed, without spots, 35–90 cm; glands yellow-green to gold, 0.2–1 mm diam. |
terete, without spots, to 200 cm; nodal glands absent. |
Turions | terminal, abundant, 3.5–7.8 cm × 2.3–5.1 mm, soft; leaves ± 2-ranked; outer leaves 3–4 per side, base not corrugate, apex apiculate to obtuse; inner leaves undifferentiated. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, flaccid; stipules persistent, inconspicuous, convolute, free from blade, white, not ligulate, 0.6–1.8 cm, fibrous, rarely shredding at tip, apex obtuse; blade light green to somewhat reddish, linear, not arcuate, 3–8.2 cm × 1–3.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse or round-apiculate, lacunae in 1–3 rows each side of midrib; veins 3. |
submersed and floating or floating absent, ± spirally arranged. |
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). |
|
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. |
|
Inflorescences | unbranched, emersed; peduncles not dimorphic, axillary, erect, rarely recurved, cylindric, 0.8–1.9(–4.2) cm; spike not dimorphic, cylindric, 8–13 mm. |
unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect, cylindric, 3–10(–16) cm; spikes not dimorphic, cylindric, 10–35 mm. |
Fruits | sessile, olive-green to brown, obovoid, turgid, abaxially keeled or not, laterally keeled or not, 2.5–3.6 × 1.7–2.4 mm, lateral keels when present without points; beak erect, 0.8–1 mm; sides without basal tubercles; embryo with 1 full spiral. |
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. |
Rhizome(s) | absent. |
present. |
2n | = 26. |
= 52. |
Potamogeton obtusifolius |
Potamogeton alpinus |
|
Phenology | Flowering and fruiting summer–fall. | Flowering early summer–fall. |
Habitat | Medium- to low-alkaline waters of lakes and slow-flowing streams | Ponds, lakes, and slow-moving streams |
Elevation | 50–2000 m (200–6600 ft) | 400–2500 m (1300–8200 ft) |
Distribution |
AK; CT; ID; MA; ME; MI; MN; MT; NH; NJ; NY; PA; RI; VT; WA; WI; WY; AB; BC; MB; NB; NB; NF; NS; NT; ON; PE; QC; SK; YT; Eurasia
|
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
|
Discussion | Potamogeton obtusifolius is a distinctive linear-leaved species with the leaf blades round at the apex, especially when fruiting inflorescences 5–7 mm wide are present. This is unusually wide for one of the linear-leaved species. Two hybrids, Potamogeton obtusifolius × P. pusillus (= P. × saxonicus Hagström) and P. friesii × obtusifolius (= P. × semifructus A. Bennett ex Ascherson & Graebner), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton |
Sibling taxa | ||
Synonyms | P. alpinus subsp. tenuifolius, P. alpinus var. subellipticus, P. alpinus var. tenuifolius, P. tenuifolius, P. tenuifolius var. subellipticus | |
Name authority | Mertens & W. D. J. Koch: in J. C. Röhling et al., Deutschl. Fl., ed. 3 1: 855. (1823) | Balbis: Misc. Bot. 13. (1804) |
Web links |
|