Abstract: A karyomorphological study of the monotypic genus of Sladenia is studied and compared with those of the supposedly related families, such as Actinidiaceae, Theaceae sensu stricto, and Ternstroemi-aceae. It confirms that chromosome number of Sladenia is 2n = 48. Sladenm has 2A karyotpye with a kaiyotypic formula of 2n = 4x = 48 = 4M + 36m + 8sm. Its interphase nucleus is characteristic of densely diffuse type. The condensation behavior of chromosomes during mitotic prophase conforms to the interstitial type. Comparative kaiyotype reveals that Sladenia is different from the related families not only in the ba-sic number, but also in the size and morphology of metaphase chromosomes, the structure of interphase nuclei, condensation behavior of chromosomes during mitotic prophase, and presence or absence of the satellite and the nucleolar organizing region as well as. These dissimilarities indicate that Sladenia is far from Actinidiaceae, TTieaceae sensu stricto. Moreover, the karyomorpholgical study shows that SMenia is not close to Temstroemiaceae, which was achieved by the previously molecular data.

Key words: Sladenia

摘要： 研究了单型属毒药树属Sladenia的核型，并与被认为有关的狭义山茶科、厚皮香科和猕猴桃科等进行了核型比较。毒药树属的体细胞中期染色体数目为2n=48，核型公式2n=4x=48=4M+36m+8sm，核型为2A型，没有发现随体和次缢痕。体细胞间期核为浓密分散型，前期核为中间型。结果表明，毒药树属与相关类群不但在染色体基数上有差异，而且在染色体大小、核型、间期核、前期核以及随体的有无等方面都不尽相同。研究结果不支持目前分子研究的观点，即把毒药树属放在厚皮香科，且认为它与猕猴桃科和狭义山茶科的亲缘关系也较远。

关键词: 毒药树属, 核型, 染色体数目