Plants collected in Wisconsin during September, 1970 were identified as P. ramosissimum and P. tenue according to the taxonomic characters established by Styles for European species of genus Polygonum and adapted for the North American species fo this genus by Mertens and Raven. The chromosome number for these two plants were determined to be 2n=60 for P. ramosissimum and 2n=30 or 32 for P. tenue. These counts were compared with chromosome numbers for Polygonum species for all of which the haploid count is either twenty or thirty. Chromatographic analysis of free amino acids and secondary substances further suggests that P. ramosissimum is properly assigned to section Polygonum while P. tenue should be placed in some other section of genus Polyyonum.