The paper is a cytological part of hiosystematic studies on Clematis L. in China. Chromosomal numbers and karyotypes of 6 spp. are reported. The results are summarized in Table 1. The chromosomal numbers and karyotypes of 2 species are first reported. The basic number of chromosomes in the genus is mainly 8(x=8), but that of C.flammula (2n=18)and C.paniculata(2n=36) is 9 (x=9)(Roy et al., 1971), an unique one in the genus.The chromosomes are middling, varying between 4.5—10.7μm; pairs 1—5 are submetacentric; pairs 6 are subterminal, pairs 7—8 are varying between subterminal to terminal ones. And one or two pairs of sat-chromosmes attached by a thin strand of chromatin material to their short arms.The results show two evolutionary trend in karyotypes of the genus: number variation(including polyploidy and aneuploidy)and structural variation. The latter is mainly in this genus, and evolution in diploids level.In addition, the first pairs of (m) chromosomes in three plants were heteromophic ones, which probably resulted from the deficiency.
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