Much like no. 1 [Potamogeton filiformis Pers.], avg coarser; tubers 3-5 cm; lvs 1-2 mm wide; stipular sheaths (at least of the primary lvs) subinflated, 2-3 times as thick as the stem, 2-5 cm, open to the base; spike with 5-12 nearly equidistant whorls of fls, 3-8 cm at maturity; fr 3-3.5 mm; 2n=78. Deep, alkaline or brackish waters; circumboreal, in Amer. s. to N.J., Mich., N.D., and Utah.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.