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potamot de l'ilenissei, Yenisei River pondweed, Yenissei River pondweed

flat-stalk pondweed, Fries' pondweed, potamot de Fries

Cauline stems

compressed-filiform, without spots, to 50 cm;

glands white, 0.3–0.5 mm diam.

compressed, without spots, 10–135 cm;

glands green, greenish brown, or gold, to 0.7 mm diam.

Turions

lateral, common, 3.5–9.5 cm × 2–5 mm, soft;

leaves ± 2-ranked;

outer leaves 3–4 per side, base not corrugate;

inner leaves undifferentiated.

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

submersed, ± spirally arranged, sessile, flaccid;

stipules deliquescent, inconspicuous, convolute, free from blade, pale brown, not ligulate, 1–2 cm, not fibrous, not shredding, apex obtuse;

blade dark green, linear, not arcuate, 3.5–9.5 cm × 1.5–2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, rounded or nearly acute to mucronate, lacunae in 1–2 rows each side of midvein;

veins 9–17.

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).

Inflorescences

unbranched, emersed;

peduncles not dimorphic, axillary, erect, cylindric, 1.7–3.5 cm;

spikes not dimorphic, cylindric, 10–30 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, reddish brown, oblong-obovoid, compressed, abaxially ridged, not laterally keeled, 3–4 × 1.5–2 mm;

beak nearly erect, 0.3–0.5 mm;

sides without basal tubercles;

embryo with 1 full coil.

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.

Rhizome(s)

absent.

absent.

2n

= 26.

Potamogeton subsibiricus

Potamogeton friesii

Phenology Fruiting early summer–late summer. Flowering and fruiting summer–fall.
Habitat Shallow water of ponds and lakes Calcareous to brackish waters of lakes and slow-flowing streams
Elevation 0–915 m (0–3000 ft) 0–3100 m (0–10200 ft)
Distribution
from FNA
AK; MB; NT; NU; ON; QC; YT; Siberia
[BONAP county map]
from FNA
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
[WildflowerSearch map]
[BONAP county map]
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.)

Source FNA vol. 22. FNA vol. 22.
Parent taxa Potamogetonaceae > Potamogeton Potamogetonaceae > Potamogeton
Sibling taxa
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, P. friesii, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. ogdenii, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. tennesseensis, P. vaseyi, P. zosteriformis
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. ogdenii, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
Synonyms P. porsildiorum
Name authority Hagström: Kongl. Svenska Vetenskapsakademiens Handlingar n.s. 44:555(5):84. (1916) Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845)
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