Echinodorus berteroi (Spreng.) Fassett
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Erect annual, slender or often robust, 1–6 dm; lvs erect, long-petiolate, with ± ovate, basally ± cordate blade mostly 4–20 × 2–12 cm, or in small forms the blade smaller, more lanceolate, and tapering to the base, in submersed forms the blade very thin and crisped; pellucid lines of the lvs (visible in transmitted light) mostly less than 1 mm apart and often several mm long; scape simple or branched, with usually several or many whorls of 3–8 fls on stiffly ascending pedicels; bracts lanceolate or linear, 3–6 mm; sep ovate, acute, 4–5 mm, ± reflexed in fr, the veins smooth, scarcely raised; pet white, broadly ovate, 5–10 mm; stamens (9)12 or more; anthers 0.5–0.8 mm; versatile; achenes 40+, brown, 2.5–3.5 mm, the erect to oblique beak 0.5–1 mm, up to half as long as the body, the fruiting head 3–7 mm thick, echinate in profile; each side of the achene with 5 arching ribs, 2 of them wing-like and alternating with the others, the keel entire; each side of the nutlet with a lanceolate, acuminate gland toward the top, entering the base of the beak. In swamps and ditches; often on sandy soil; C. Amer. and W.I. to Calif., Tex., and n. in the Mississippi R. drainage to O., Ill., and S.D. June–Oct. (E. rostratus; E. cordifolius, misapplied) Our plants, as here described, are var. lanceolatus (Engelm.) Fassett.