Abstract: In this paper the chromosome numbers of Yinshania and Hilliella are studied for expressing the systematic rela tionship and the classification problem of both genera. The chromosome numbers as follows:Yinshania:furcatopilosa, 2n=12; Y.henryi, 2n=12; Y.qianningensis, 2n=12; Y.acutangula, 2n=14. Hilliella changhuaensis, 2n=42; H.paradoxa, 2n=44; H.shuangpaiensis, 2n=44; H.sinuata, 2n=42; H.yixianensis, 2n=42. The chromosome numbers, morphology and geographical distribution support dealing with Yingshania and Hilliela as two independent genera respectively. A key to related genera is given. Yinshania is endemic to China. Analysis of the evolutionary trends of some characters shows that the Sect. Yinshania is primitive, and the Sect. Microcarpae is advanced. After investigating the distribution pattern of the genus, it is considered that Western Sichuan and its adjacent area is the center of differentiation and distribution of Yinshania in recent times. Yinshania perhaps originated from this area, differentiated and migrated by the Himalaya orogenesis and by a series of world-wide climatic fluctuations.

Key words: Yinshania, Classification, Chromosome mumbers, Geog raphical distribution