The monotypic genus Tamia was described by Ravenna in 2001 based on specimens of Calydorea pallens from Bolivia and West-Central Argentina (excluding Córdoba and San Luis). At the same time, Ravenna described Calydorea undulata as a new species to accommodate the excluded specimens. He used floral morphology to segregate Tamia from Calydorea. He described Calydorea as having the anthers twisted/circinate after dehiscence, whereas in Tamia, the anthers are straight. Similarly, in Tamia the upper third of the anther is adnate to the style arms while in Calydorea the anthers are free from the style branches. We here evaluate the validity of Tamia and C. undulata based on morphological and cytological approaches. An examination of living plants of both taxa showed the anthers to be straight during dehiscence and twisted when the pollen was exposed, likewise the stamens were completely free from style branches in both taxa. Both have a base chromosome number of x = 7 (C. undulata diploid, 2n = 14; T. pallens tetraploid, 2n = 28). The karyotype formula for C. undulata was 5 m + 2 sm and 7 m + 7 sm for T. pallens. The karyotype is bimodal in C. undulata and moderately asymmetrical in T. pallens. These chromosomal differences and differences in petal shape (the outer are flat for both taxa while the inner are geniculate in T. pallens but flat with undulate margins in C. undulata) and flower color (pale lilac with dark violet dots in T. pallens and violet-blue with violet stripes in C. undulata) suggest that these taxa are distinct species of Calydorea, where a polyploid series based on x = 7 is known. The divergence of their karyotypes is within the observed chromosomal variability of genera in Iridaceae. Thus, we conclude that Tamia should be regarded as a synonym of Calydorea, with the return of its species to Calydorea pallens, because the floral differences between them are not enough to merit generic segregation. Calydorea undulata is nonetheless a valid species.