In Flora Iranica area, Tanacetum comprised 18 sections and 54 species. Considering new findings, Tanacetum species in Iran has been increased to 37. No detailed information on the karyotype analysis of the studied species was found in the literature. Therefore, in the present study, the detailed karyomorphology of six populations belonging to five taxa of Tanacetum sect. Xanthoglossa were studied. The basic chromosome number of the Tanacetum has been reported to be x=9. Mitotic chromosome number of studied taxa were found to be diploid (2n=2x=18) for T. argyrophyllum, T. oligocephalum (Khoy), T. uniflorum (no previous karyological records are known for this species) and T. pinnatum. According to the symmetry classes of Stebbins, class 2A was found predominant karyotype class among the studied Tanacetum except for tetraploid (2n=4x=36) T. polycephalum subsp. Heterophyllum which was placed in 2B. Karyotype analysis of each taxon has been presented and discussed.
