Abstract: Ahstract Sequoia sempervirens is an autoallopolyploid with the genomic formtlla AAAABB. Its complement--AA and --B, that belong to Stebbins' "1A" and "1B" karyotypic type respectively, are quite similar to the karyotypes of Metase- quoia glyptostroboides and Seql,oiadendron giganteum (Table 1, 2 ). So some ancient species of Metasequoia and Sequoiadendron may be the two hybrid parents of S. sempervirens, M. glyptostroboides and S. giganteum arc pro- bably direct descendants of them. The present study supports Stebbinsl stlggestion that one ancient species of Metasequoia would be an ancestor of S. sempervi- rens, but does not agree with his hypothesis that another ancestor is extinct and has not left close relatives. The original process of S. sempervirens may be shown. as Fig. l.

Key words: Karyotype