Much like no. 1 [Alisma triviale Pursh], but with smaller fls; sep 1.5-2.3 mm; pet 1.8-2.5 נ1.4-2.0 mm, barely or scarcely longer than the sep; anthers 0.4-0.6 mm; style very short, 0.2-0.4 mm; achenes 1.5-2.2 mm; 2n=14. Usually in shallow water; Vt. and Mass. to N.D., s. to Fla. and Tex. (A. plantago-aquatica var. parviflorum) Variously reported to intergrade with no. 1 or to be genetically isolated from it.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.