Anatomical Study of the Stems of the 10 Selaginella Species and Its Taxonomic Significance

Using the samples collected from Hubei Province and its neighboring region,the anatomical structures of the stems of 10 Selaginella species were observed under light microscope.The results showed that 10 species share some common anatomical characters:(1) The epidermis cells are more or less increased in thickness of the walls.(2) The cortex usually own mechanical tissue,fiber bundles and thick-walled cells(generally only the later).(3) Inside the endodermis,there generally is a large air chamber,with a stele hanged in its central part by the some cross-bridges.(4) The stele is enclosed by the pericyle ring made up of one or more layers of thin-walled cells.(5) The vascular bundle is amphicribral.However,certain significant anatomical differences exist among the 10 species.Whether several features exist would provide significant basis for classification and identification of the 10 species,including ridged heaves outside the epidermis of the stem,the fiber bundles in the cortex,the thick-walled cells in the outer cortex.The shape and number of the air-chamber,stele,xylem and thin-walled cells forming the cross-bridge also are significant characters for classification.Whatmore,microscopic characteristics can also be used to resolve some difficult problems of taxonomy only based on morphological analysis,and to deduce the relationships among some Selaginella species.