Potamogeton friesii |
Potamogeton oblongus |
|
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flat-stalk pondweed, Fries' pondweed, potamot de Fries |
cinnamonspot pondweed, potamot oblong |
|
Cauline stems | compressed, without spots, 10–135 cm; glands green, greenish brown, or gold, to 0.7 mm diam. |
terete, without spots, 5–30 cm; nodal glands absent. |
Turions | 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. |
absent. |
Leaves | 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). |
both submersed and floating or only submersed, ± spirally arranged. |
Floating leaves | petioles continuous in color to apex, 1–17 cm; blade adaxially reddish brown, ovate, 3–8(–10) cm × 10–46 mm, base rounded or slightly cordate, apex obtuse, acute, or somewhat apiculate; veins (11–)15–19(–21). |
|
Submersed leaves | petiolate, lax; stipules persistent, conspicuous, convolute, free from blade, greenish, not ligulate, to 3 cm, not fibrous, not shredding at tip, apex acute; petioles 1–3(–8) cm; blade dark green, lanceolate to occasionally ovate, occasionally arcuate, 3–13 cm × 4–15(–44) mm, base acute, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae in 2–4 rows each side of midvein; veins 7–11. |
|
Inflorescences | 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. |
unbranched, emersed; peduncles not dimorphic, erect to slightly recurved, cylindric, 4–12 cm; spikes not dimorphic, cylindric, 20–40 mm. |
Fruits | 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. |
sessile, dark reddish brown, obovoid to orbicularoid, compressed, not abaxially or laterally keeled, (1.6–)2–2.5 × (1.2–)1.5–2.1 mm; beak minute or obsolete, recurved; sides without basal tubercles; embryo with 1 full spiral. |
Rhizome(s) | absent. |
present. |
2n | = 26. |
= 26. |
Potamogeton friesii |
Potamogeton oblongus |
|
Phenology | Flowering and fruiting summer–fall. | Flowering July–August. |
Habitat | Calcareous to brackish waters of lakes and slow-flowing streams | Acid to neutral waters of ponds, lakes, and occasionally streams |
Elevation | 0–3100 m (0–10200 ft) | 10–100 m (0–300 ft) |
Distribution |
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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NF; NS; SPM; Europe; n Africa; Atlantic Islands (Azores) [Introduced in North America] |
Discussion | 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.) |
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Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton |
Sibling taxa | ||
Name authority | Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845) | Viviani: Annali di Botanica 1(2): 102. (1802) |
Web links |