Cleaning orthographic variants of the same name. Engelmann originally published the name as "N. polysepalum", but the gender was corrected subsequently. See Calflora (http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=10994), WA Flora Checklist (http://biology.burke.washington.edu/herbarium/waflora/checklist.php?Taxon=Nuphar%20polysepala&ID=4938), and Tropicos (http://tropicos.org/Name/22600083).