J Integr Plant Biol. ›› 1990, Vol. 32 ›› Issue (10): -.

• Research Articles •    

The Anatomical Study of Plagiozamites oblongifolius and the Systematic Position of Plagiozamites

Guo Ying-ting, Tian Bao-lin and Han De-xin   

Abstract: The specimens of petrified fossil plant, Plagiozamites oblongifolius, described here, were collected from the sandstone of Late Permian of Western Guizhou, China. Their morphological as well as the internal anatomical characters were preserved. All of the samples were treated with hydrochloric acid and made into peels and thin sections. The main internal anatomical characters are as follows: The mesophyll of pinna is not differentiated into spongy and palisade tissue. The phloem of the pinna vein is ectophloic and the xylem of which is exarch. The tracheids are annular, helical and scalariform thickening. The vein is surrounded by the transfusion tissue which consists of parenchymous cells and short tracheids. In the transverse section of rachis, the vascular bundle is in "U" shape. It has amphiphloic siphonostele with exarch xylem. The protoxylem consists of small tracheids with spiral or annular thickened walls, and the metaxylem, with scalariform or transitional type of scalariform and pitting thickening. The structure of vascular bundles of the pinna and the rachis is similar to that of Cycas (Fig. 1, 2). The systematic position of Plagiozamites has been disputed for a long time. However, based on the morphological and anatomical characters of Plagiozamites, they might be belonged to cycadophytes. If the fructifications of Plagiozamites are considered as the same type as that ef Noeggerathia, Plagiozamites should be a kind of progymnosperms.

Key words: Plagiozamites oblongifolius, Anatomical characters, Systematic position

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