Middle cauline lvs 20-180 times as long as wide, mostly 0.3-1.5 (avg 0.5+) mm wide; floating lvs 3-17-veined, 2-20 mm wide; widespread, but in our range n. only to Mass., s. N.Y., n. O., and c. Minn. (P. capillaceus; P. hybridus, misapplied)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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