The Anatomy Of The Permineralized Seed Ferns Stem From The Late Permian In Panxian,Guizhou Province

The seed ferns,a group of early gymnosperms emerged during the early Devonian period,flourished in the Carboniferous and Permian and extinct during the Mesozoic.but seeds are seen.Today,these plants have been found in many parts of the world.In the Late Permian strata of the panxian mining area in the west of Guizhou in the southwestern part of China,there are rich and well-preserved seed fern plant fossils with anatomical structures.The current international research on permineralized plants is widely used Membrane technique was used to study the stem fossils of five seed fern plants collected from the Late Permian strata in the mining area of Panzhou City.Stalk fossils are considered to belong to Callistophyton boyssetii.Since the specimens were well preserved,in addition to the general characteristics of C.boyssetii,in addition to the general features of C.boyssetii,there are some features that have not previously been reported.The number of exarch vascular bundles in the eustele of the C.boyssetii immature stem is slightly changed in different specimens.The posterior xylem of some vascular bundles has a joint phenomenon in the development process,which is different from the development model proposed by Rothwell(1975).Brown matter are in a small number of metaxylem.In secondary development,outside vascular bundles and Between the vascular bundles activitie secondary developmental at the same time,but the secondary xylem tracheids outside primary vascular bundle were larger in development and smaller in number than those in bundle.The secondary xylem has nearly storied tracheids with bordered pits that are commonly multiseriate,alternately arranged.The number of bordered pit is variable and more than 4~8 columns,and the number of columns on the same secondary xylem is also variable.In the early development of secondary xylem,the newly increased secondary xylem tracheids are always located between the rays.At a certain distance of the stem,with the increase of the number of the secondary xylem,the rays only extend radially on the original rays without adding new rays.Pericytes small,nearly equiaxed,part of the inner tangential wall and radial wall thickening.The cortex is of the Sparganum type in which the resinous pathways with epithelial cells are distributed rather than the previously considered secretory or secretory cells.There is a brown material in the resin canal,and the number of resin canal s in different samples is also variable.There are cortical appendages on the stem,and the appendages are spirally arranged on the stem.By comparison,there are many similar characteristics between C.boyssetii and Aculeovinea yunguiensis.It is speculated that A.yunguiensis may be C.boyssetii or varietas.The discovery of Vesicaspora,the pollen of the Callistophytales plant in the Late Permian strata of Weining,Guizhou,and the discovery of C.boyssetii fossils in the Late Permian strata of Huopu,YueLiangtian,and Shanjishu in Panxian,Guizhou Province,shows that these plants still have a certain distribution in the western part of Guizhou at that time.However,with the end of the Paleozoic era,the ornate Callistophytales plants in western Guizhou probably did not last into the Mesozoic Era.