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.