Potamogeton friesii |
Potamogeton zosteriformis |
|
---|---|---|
flat-stalk pondweed, Fries' pondweed, potamot de Fries |
eel-grass pondweed, flat-stem pondweed, potamot zostériforme |
|
Rhizomes | absent. |
absent. |
Cauline stems | compressed, without spots, 10–135 cm; glands green, greenish brown, or gold, to 0.7 mm diam. |
conspicuously flattened ("wing-flattened"), without spots, 60–120 cm; glands absent or rarely present, when present, gold, 0.3 mm diam. |
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. |
common, terminal or lateral, 4–7.5 × 2–4.5 cm, firm; leaves ± 2-ranked; outer leaves 3–4 per side, base not corrugate, apex acute; inner leaves undifferentiated. |
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). |
submersed, ± spirally arranged, sessile, rigid; stipules persistent, conspicuous, convolute, free from blade, white, not ligulate, 1.5–3.5 cm, fibrous, shredding at tip, apex obtuse to acuminate; blade light green, linear, not arcuate, 10–20 cm × 2–5 mm, base rounded, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, blunt, acuminate, or bristle-tipped, lacunae absent; veins 15–35. |
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, terminal, erect to ascending, occasionally recurved, cylindric, 2–5 cm; spikes not dimorphic, cylindric, 15–30 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. |
light green to olive-green, quadrate-oblong or nearly orbicular, turgid, sessile, with abaxially keeled, not laterally keeled, 4–5 × 3–3.5 mm, keel winglike; beak erect, 0.6–1 mm; sides without basal tubercles; embryo with 1 full spiral. |
2n | = 26. |
= 52. |
Potamogeton friesii |
Potamogeton zosteriformis |
|
Phenology | Flowering and fruiting summer–fall. | Flowering summer–fall. |
Habitat | Calcareous to brackish waters of lakes and slow-flowing streams | Lakes, ponds, and slow streams |
Elevation | 0–3100 m (0–10200 ft) | 0–15003000 m (0–49222400 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
|
AK; CA; CT; IA; ID; IL; IN; KS; MA; ME; MI; MN; MT; ND; NE; NH; NJ; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; YT
|
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.) |
One hybrid, Potamogeton zosteriformis × P. strictifolius, has been described and has been given the name P. ×haynesii Hellquist & G. E. Crow and is known from northern Michigan, Minnesota, Vermont, and southern Canada. (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. zosterifolius subsp. zosteriformis, P. zosterifolius var. americanus | |
Name authority | Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845) | Fernald: Memoirs of the american academy of arts and science n.s. 17:36. (1932) |
Web links |
|