Egeria densa Planch.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Principal lvs in whorls of 4–6, oblong or broadly linear, 12–40 × 1.5–5 mm, spreading, the internodes short; staminate spathes 11–13 mm, deeply cleft down one side; hypanthium becoming 3–6 cm, the sep 3–4 mm, the pet 9–11 mm; pistillate plants with smaller pet, rare, unknown in our cult. and escaped plants; 2n=48. Native from se. Brazil to n. Arg., commonly cult. in aquaria and occasionally established in ponds in our range. (Anacharis d.; Elodea d.)