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long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed

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

Cauline stems

terete, without spots, to 210 cm;

nodal glands absent.

compressed-filiform, without spots, to 50 cm;

glands white, 0.3–0.5 mm diam.

Turions

absent.

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.

Leaves

submersed, ± spirally arranged, sessile, lax;

stipules persistent, conspicuous, convolute, free from blade, white to green, not ligulate, 3–8.1 cm, fibrous, shredding at apex;

blade pale green, rarely olive green, linear-lanceolate, not arcuate, 0.8–2.8 cm × 11–46 mm, base clasping, without basal lobes, margins entire, rarely crispate, apex hoodlike, splitting when pressed, obtuse, lacunae absent;

veins 11–33.

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.

Inflorescences

emersed, unbranched;

peduncles not dimorphic, terminal or axillary, erect to spreading, cylindric, 9.5–53 cm;

spikes not dimorphic, cylindric, 34–75 mm.

unbranched, emersed;

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

spikes not dimorphic, cylindric, 10–30 mm.

Fruits

sessile, greenish brown, obovoid, turgid, abaxially keeled, occasionally laterally keeled, 4–5.7 × 3.2–4 mm, lateral keels when present without points;

beak erect, 0.6–1 mm;

sides without basal tubercles;

embryo with 1 full spiral.

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.

Rhizome

present.

absent.

2n

= 52.

Potamogeton praelongus

Potamogeton subsibiricus

Phenology Flowering summer–fall. Fruiting early summer–late summer.
Habitat Neutral to alkaline waters of lakes, rivers, and streams Shallow water of ponds and lakes
Elevation Greenland; 100–3000 m (Greenland; 300–9800 ft) 0–915 m (0–3000 ft)
Distribution
from FNA
AK; CA; CO; CT; IA; ID; IN; MA; ME; MI; MN; MT; NE; NH; NJ; NY; OR; PA; SD; UT; VT; WI; WY; AB; BC; MB; NB; NF; NS; NT; NU; ON; PE; QC; SK; YT; Mexico; Greenland; Eurasia
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; MB; NT; NU; ON; QC; YT; Siberia
[BONAP county map]
Discussion

Potamogeton praelongus is one of the easiest pondweeds to identify with its submersed leaves only clasping the more or less zigzagged stem. The persistent, hugelarge, white stipules provide another clue to this species.

Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. alpinus × P. praelongus (= P. × griffithii A. Bennett), P. crispus × P. praelongus (= P. × undulatus Wolfgang ex Schultes & Schultes f.), and P. gramineus × P. praelongus (= P. × vilnensis Galinus), 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. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, 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. 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
Synonyms P. porsildiorum
Name authority Wulfen: Arch. Bot. (Leipzig) 3: 331. (1805) Hagström: Kongl. Svenska Vetenskapsakademiens Handlingar n.s. 44:555(5):84. (1916)
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