Reported in this paper was the karyomorphology of the monotypic genus Po-
matosace Maxim. The interphase nuclei and prophase chromosomes of P. filicula Maxim.
were categorized to be complex chromocenter type and interstitial type respectively; the
metaphase chromosomes were counted to be 2n = 20, ranging in length from 6.4µm to 4.1µm; the karyotype was formulated as 2n= 18m + 2sm, with the karyotype asymmetry belonging to 2A. The similar karyomorphological characteristics of interphase nuclei and prophase chromosomes between Pomatosace and Androsace, together with the similar sizeand morphology of their metaphase chromosomes, support the viewpoint that they are closelyrelated.