Isoetes engelmannii A.Braun
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Lvs 6–35(–50) cm × 0.6–2 mm, erect, not twisted, with abundant stomates and usually 4 peripheral strands; sporangia 6–13 mm, pale, one-third to two-thirds covered by the velum; megaspores 0.35–0.6 mm wide, raised-reticulate; 2n=22. Amphibious, submersed in spring, usually later emersed; N.H. to Fla., w. to Ind., Ill., se. Mo., and Miss.