Phylogenetic anatomy of the Cretaceous Cycadophytes.

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We have examined anatomy of the Cretaceous cycadophytes as a basic studies to elucidate the origin of angiosperms. 1)Nishida, Harufumi has studied histology and organography of flowers of Bennettitales from Hokkaido and Chiba Prefecture. (1)He has examined exact structure of flowers of Cycadeoidea, a big member of the order, and Cycadeoidella, a small member of the order, and elucidated that the ovules of Bannettitales are enveloped by a one cell-layered sheath. (2)He found out vascular strand in the integument of Cycadeoidella, which has never been examined in Bennettitales so far. (3)He also examined vascular strand in the walls of synangium of Cycadeoidella, Which has also never been known in this, order so far. (4)He has proposed a new organographycal hypothesis that the walls of synangium and ovular sheath of Bennettitales originate in ultimate segments of pinnules of bennettitalean fronds(Nishida, H., 1991).2)NISHIDA, Makoto has examined anatomy of. some vegetative organs of the Cretaceous cycadophytes. (1)He has reviewed histologically four species of cycadeoidean trunks from Hokkaido, and in addition, he described a big cycad trunk from Gunma Prefecture as a new genus(Nishida et al., 1991). (2)He also examined a petrified petiole and a slender trunk from Hokkaido, which closely resemble living Cycad. These findings are the first records of petrified cycads in Japan.