Potamogeton nodosus |
Potamogeton friesii |
|
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loddon's pondweed, long-leaf pondweed, pondweed, potamot noeuex |
flat-stalk pondweed, Fries' pondweed, potamot de Fries |
|
Rhizomes | present. |
absent. |
Cauline stems | terete, without spots, to 100 cm; nodal glands absent. |
compressed, without spots, 10–135 cm; glands green, greenish brown, or gold, to 0.7 mm diam. |
Turions | absent. |
terminal or lateral, common, 1.5–5 cm × 1.5–4 mm, soft; leaves ± 4-ranked; outer leaves 2–3 per side, base corrugate, apex apiculate to acute; inner leaves reduced, arranged into fan-shaped structure and oriented at 90° angles to outer leaves. |
Leaves | both submersed and floating, or floating absent, ± spirally arranged. |
submersed, ± spirally arranged, delicate to rigid, sessile; stipules not persistent, inconspicuous, convolute, free from blade, white, not ligulate, 0.55–2.1 cm, fibrous, coarse, shredding at tip, apex obtuse; blade light green, rarely olive-green to.somewhat reddish, linear, not arcuate, 2.3–6.5 cm × 1.2–3.2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or 1 narrow row each side of midrib; veins 5–7(–9). |
Floating leaves | petioles 3.5–26 cm; blade adaxially light green, lenticular to elliptic, 3–11 cm × 15–45 mm, base cuneate to rounded, apex acute to rounded; veins 9–21. |
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Submersed leaves | petiolate, lax; stipules persistent to deliquescent, conspicuous, convolute, free from blade, light brown, not ligulate, 3–9 cm, not fibrous, not shredding at tip, apex round to acute; petioles 2–13 cm; blade light to dark green, linear-lanceolate to lance-elliptic, not arcuate, 9–20 cm × 10–35 mm, base acute, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, without sharp awl-like tip, lacunae in 2–5 rows each side of midrib; veins 7–15. |
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Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal, erect to ascending, cylindric, 3–15 cm; spikes not dimorphic, cylindric, 20–70 mm. |
unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect or rarely recurved, slightly clavate, 1.2–4.1(–7) cm; spike not dimorphic, cylindric, 7–16 mm. |
Fruits | sessile, red to reddish brown, obovoid, abaxially keeled, laterally ridged, 2.7–4.3 × 2.5–3 mm, keel well developed, lateral ridges with blunt to sharp tips; beak erect; sides without basal tubercles; embryo with 1 full spiral. |
sessile, olive-green to brown, obovoid, turgid, not abaxially or laterally keeled, 1.8–2.5 × 1.2–2 mm; beak erect, 0.3–0.7 mm; sides without basal tubercles; embryo with 1 full spiral. |
2n | = 52. |
= 26. |
Potamogeton nodosus |
Potamogeton friesii |
|
Phenology | Flowering summer–fall. | Flowering and fruiting summer–fall. |
Habitat | Clear to turbid waters of lakes, streams, rivers, and sloughs | Calcareous to brackish waters of lakes and slow-flowing streams |
Elevation | 0–3300 m (0–10800 ft) | 0–3100 m (0–10200 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; NB; ON; QC; SK; Mexico; Central America; South America; West Indies; Eurasia
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AK; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NY; OH; PA; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; YT; Eurasia
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Discussion | Six hybrids, Potamogeton gramineus × P. nodosus (= P. × argutulus Hagström), P. illinoensis × P. nodosus (= P. × faxonii Morong), P. nodosus × P. richardsonii (= P. × rectifolius A. Bennett), P. natans × P. nodosus (= P. × schreberi Fischer [P. × perplexus A. Bennett]), P. alpinus × P. nodosus (= P. × subotusus Hagström), and P. epihydrus × P. nodosus (= P. × subsessilis Hagström), have been described. Potamogeton nodosus is a common floating-leaved species throughout much of the United States and southern Canada. When both submersed and floating leaves are present, it is very easily recognized by the petioles of the submersed leaves being longer than 5 cm. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potamogeton friesii is a fairly common linear-leaved species, especially of calcareous waters of lakes and streams of the upper Midwest. Whenever turions are present, the species is easily identified, as it is the only one with the outer leaves of the turions having corrugate bases and the inner leaves turned at right angles to the outer leaves. Two hybrids, Potamogeton friesii × P. pusillus (= P. × pusilliformis Fischer [P. × intermedius Fischer]) and P. friesii × P. obtusifolius (= P. × semifructus A. Bennett ex Ascherson & Graebner), 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 | ||
Name authority | Poiret: in J. Lamarck et al., Encyclopedie Methodique. Botanique... Supplement 4(2): 5354. (1816) | Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845) |
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