Abstract: There are about 10 species of Ostericum in the world, of which seven are distributed in China. The present paper deals with the karyotypes of five species and one variety (covering 13 populations) within this genus. The karyotype formulae are as follows: O. citriodorum (Hance) Yuan &Shan 2n=22= 16m+ 6sm (Baoan, Guangdong) and 2n= 22=14m + 6sm + 2st(Yingtan, Jiangxi); O. huadongensis Z. H. Pan & X. H. Li 2n = 22 =16m + 6sm (Nanjing, Jiangsu, cultivated) and 2n= 22 = 16m + 4sm + 2sm (SAT) (Guangde,Anhui); O. viridiflorum (Turcz.) Kitagawa 2n = 22 = 18m + 4sm (Ergun Youqi, Nei Mongol) and 2n = 22 = 18m + 2sm + 2st (SAT) (Shuangyashan, Heilongjiang); O. sieboldii (Miq.) Nakai 2n = 22 = 4sm + 16st + 2st (SAT) ( Zhuanghe, Liaoning ); and 2n = 22 = 2sm + 20st (Changbaishan, Jilin); O. sieboldii var. praeteritum (Kitagawa) Huang 2n = 22 =2sm+ 20st (Anshan, Liaoning); O. grosseserratum (Maxim.) Kitagawa 2n = 18 = 2sm +16st (Zhuanghe, Liaoning), 2n = 18 = 2sm + 16st (Yixing, Jiangsu), 2n = 18 = 18st(Guangde, Anhui) and 2n= 18=18st (Tianmushan, Zhejiang). The karyotypes of O. citriodorum, O. huadongensis and O. viridiflorum belong to 2A, while those of O. sieboldii and O. grosseserratum belong to 4A. Besides, O. grosseserratum has decreasing chromosome number (n = 9), which is very unique in the tribe Peucedaneae.Based on the karyotypes and geographical distribution of the species, as well as gross morphology and pollen morphology, we considered that there might be two secondary diversity centres of Ostericum in NE and E China, which have developed and migrated from the Hengduanshan region, the origin and diversity center the of related genus-Angelica.

Key words: Ostericum, Karyotype, Geographical distribution, China