摘要
本文根据对椭圆斜羽叶(Plagiozamites oblongifolius)钙质石化化石的研究,认为其主要特征如下:羽状复叶,叶肉无海绵组织和栅栏组织分化。羽片叶脉维管束外韧式,木质部外始式,与现代苏铁属叶脉特征相近。羽轴维管束为“U”形,外始式木质部、梯状纹孔管胞,与现代苏铁属的羽轴维管束相似。根据上述特征,目前可将斜羽叶属归入原始苏铁类植物。但是,如果斜羽叶的生殖器官同 Noeggerathia 一样,为异孢型孢子囊穗,则斜羽叶可能为一种与苏铁类起源有关的原裸子植物。
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 ch- aracters 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 trach- eids 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 ra- chis,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 me- taxylern,with scalariform or transitional type of scalariform and pitting thickening.The stru- cture of vascular bundles of the pinna and the rachis is similar to that of Cycas (Fig.I,2). The systematic position of Plagiozamites has been disputed for a long time.However, based on the morphological and anatomical characters of Plagiozarnites,they might be belonged to cycadophytes.If the fructifications of Plagiozamites are considered as the same type as that of Noeggerathia,Plagiozamites should be a kind of progymnosperms.
关键词
椭圆斜羽叶
解剖
分类
Plagiozamites oblongifolius
Anatomical characters
Systematic position
