Myriophyllum verticillatum L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Much like no. 9 [Myriophyllum sibiricum Kom.]; lvs with 9–17 segments per side; floral bracts less strongly reduced and modified, those subtending the pistillate fls (1–)2–several times as long as the fl, sometimes to 1 or even 1.5 cm, even those subtending the staminate fls evidently cleft or laciniate- toothed; pistillate fls with persistent sep mostly 0.5–1 mm; staminate fls with yellow-green pet; stamens 8, less often 4; turions abscised from the stem in late fall or early winter, dark yellow-green, their lvs less modified than in no. 9; 2n=28. In acid to circumneutral waters to 3 m deep; circumboreal, s. to Mass., N.Y., Ind., Ill., Nebr., and Utah. (M. hippuroides, misapplied to the phase with 4 stamens)