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clasping-leaf pondweed, potamot perfolié

Greenland pondweed

Rhizomes

present.

absent.

Cauline stems

terete, without spots, to 250 cm;

nodal glands absent.

terete, without spots, 20–50 cm;

glands white, 0.1–0.7 mm diam.

Turions

absent.

terminal or axillary, common, 4.2–8.4 cm × 1.4–2.5 mm, soft;

leaves ± 4-ranked;

outer leaves 2 per side, base without corrugations, apex acute to apiculate;

inner leaves unmodified.

Leaves

submersed, ± spirally arranged, sessile, lax;

stipules deteriorating into fibers and deciduous, inconspicuous (absent on proximal portion of stem), convolute, free from blade, light brown to green, not ligulate, 3.5–6.5 cm, not fibrous, not shredding at apex;

blade olive-green, broadly lanceolate, orbiculate, or ovate, not arcuate, 0.9–7.6(–9.7) cm × 7–40 mm, base rounded, without basal lobes, clasping, margins entire, often crispate, apex not hoodlike, not splitting when pressed, round, rarely acute;

veins 3–25.

submersed, ± spirally arranged, sessile, delicate;

stipules deliquescent to persistent, inconspicuous, convolute, free from blade, brown, not ligulate, 0.45–1.91 cm, not fibrous, not shredding at tip, apex obtuse;

blade pale to deep green, linear, not arcuate, 2.6–8.8 cm × 0.7–1.7 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or present, 0–3 rows each side of midrib;

veins 7–11.

Inflorescences

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect to rarely recurved, cylindric, 1–7.3 cm;

spike not dimorphic, cylindric, 0.4–4.8 cm.

unbranched, emersed;

peduncles not dimorphic, terminal, erect, cylindric, 20 mm;

spikes not dimorphic, cylindric, 5 mm.

Fruits

sessile, greenish brown to olive-green, obovoid, turgid or rarely concave, not abaxially or laterally keeled, 1.6–3 × 1.3–2.2 mm;

beak erect, 0.4–0.6 mm;

sides without basal tubercles;

embryo with 1 full spiral.

not laterally keeled, 2.6–2.7 × 2 mm;

beak erect, 0.3 mm;

sides without basal tubercles;

embryo with 1 full coil.

2n

= 52.

= 26.

Potamogeton perfoliatus

Potamogeton groenlandicus

Phenology Flowering summer–fall. Flowering late summer.
Habitat Waters, often brackish, of lakes, streams, rivers, and bays Ponds and lakes
Elevation 0–100 m (0–300 ft) 10–450 m (0–1500 ft)
Distribution
from FNA
AL; CT; DC; DE; FL; LA; MA; MD; ME; NC; NH; NJ; NY; OH; PA; RI; VA; VT; NB; NL; NS; ON; PE; QC; SPM; Africa; Greenland; Eurasia; Central America (Guatemala); Australia
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from USDA
Greenland
[BONAP county map]
Discussion

Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. perfoliatus × P. pusillus (= P. × mysticus Morong), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), and P. alpinus × P. perfoliatus (= P. × prussicus Hagström), have been described.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Of conservation concern.

(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. praelongus, 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. 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. pusillus subsp. groenlandicus
Name authority Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) Hagström: Kongl. Svenska Vetenskapsakademiens Handlingar n.s. 55(5): 127. (1916)
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