Potamogeton nodosus Poir.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stem branched, to 2 m; submersed lvs thin, narrowly lanceolate to linear, to 3 dm, 1–2.5(–3) cm wide, 7–15-veined, acute, usually with a pair of conspicuous lacunar bands along the midvein, gradually tapering into a long (2–13 cm) petiole; floating lvs elliptic, 5–13 × 1–4 cm, acute or acutish, on petioles 5–20 cm; stipules axillary, free, 4–10 cm, attenuate to obtuse; peduncles 5–12 cm, stout, often thicker than the stem; spikes dense, cylindric, 3–5 cm; frs broadly semi-obovoid, 3–4 mm (including the short beak), with a sharp, narrow, often tuberculate dorsal keel sometimes flanked by 2 low ridges. Variously slow or fast, deep or shallow, often alkaline water; nearly cosmopolitan, and throughout our range. (P. americanus; ? P. fluitans)