Abstract: The ultrastructure of Azolla filiculoides was investigated by means of transmission and scanning electron microscopy .Hairs, epidermal tricho-mes, were found on the shoot tip, the mature leaf cavity and the embryo.The hair cells,during various developing stages,had some of the features transfer cells had.And the hair cells on the shoot tip and the embryo had the structural features secretory cells had. In their cytoplasm, there were abundant mitochodria, dictyosomes, rough endoplasmic reti-culum,vacuoles and secretory granules.From this it is inferred that such hair cells might be involved in supplying the nutrient substances to the non N-fixing vegtative cells and the akinets of Anabacna; that the hair cells in the mature leaf cavity might play an important role in metabolic exchange between Azolla and Anabaena; and that the difference in structure between the terminal and the basal cells might involve their difference in function.