Potamogeton pusillus Linnaeus subsp. groenlandicus (Hagström) Boch

Rhizomes absent. Cauline stems terete, without spots, 20--50 cm; glands white, 0.1--0.7 mm diam. Turions 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, 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, erect, cylindric, 20 mm; spikes not dimorphic, cylindric, 5 mm. Fruits not laterally keeled, 2.6--2.7 ´ 2 mm; beak erect, 0.3 mm; sides without basal tubercles; embryo with 1 full coil. 2n = 26.

Flowering late summer. Ponds and lakes; of conservation concern; 10--450 m; Greenland.