Abstract: Epidermal characters and anatomical structure of leaves of Sedum aizoon L. and S. spectabilis Boreau have been observed by the light microscope and the influence of the leaf anatomical structure of two species in different soil water stress were studied. The results showed that there was a strongly relationship between the morphological, anatomical structures with their drought adaptability. There have the thin cuticle and well-developed aquiferous tissues in the mature leaves of two species. And there was ambiguous differentiation between spongy and palisade tissue in mesophyll. The vascular bundle of S. spectabilis Boreau and S. aizoon L.were more developed and they have well-developed stomatic chamber which below the epidermic cell. We also discovered many idioblasts which can drank and reserved much water around the vascular bundle. These characters were the key factors for the drought tolerance of both two species.

Key words: leaf tissue structure, drought tolerance, S.aizoon L., S. spectabilis Boreau