Publication: Bemerk. Reise Russ. Reich. 1: 220. 1775.
selected vouchers: Not at WTU; WS?
Notes: Possibly extirpated.
FNA3: "Although broadly distributed in the northwest part of the flora, Nymphaea tetragona is apparently not common over the Canadian portion of its range. It was collected once in extreme northwestern Washington but is believed to be extirpated there. True N . tetragona is absent from northeastern North America and, now, from the conterminous United States, where this name has usually been applied to what is here segregated as N . leibergii . In size and shape of leaves and flowers the two taxa are very similar. They differ in the leaf mottling often present in developing leaves of N . tetragona but absent in N . leibergii ; the distinctly tetragonal appearance of the receptacle in N . tetragona ; and in the longer carpellary appendages, the presence usually of more stamens, and purple-colored stamens and pistils in N . tetragona . Only in living plants is it apparent that leaves of N . leibergii are thicker with impressed veins abaxially compared to the relatively thin leaves with raised veins in N . tetragona . Although distinctions in sepal and petal apices (often acute in N . tetragona and often rounded in N . leibergii ) were the basis for the establishment of Castalia leibergii , the characters are variable in both taxa and thus of limited utility in distinguishing them."