Abstract: Lygodium japonicum(Thunb) Sw. is one of normal medicinal ferns. Based on many previous works, its gametophytic development was studied by the microscope. We also supplemented the representative characteristic of it, such as Shorter filament was 2~3 cells long, Prothallial plate and young prothallus of develop types were diverse, Adult prothallus was Cordate-thalloid form, Hair made of 1 cell or 2 cells, Unicellular rhizoid was either in chloroplasts or at top enlargment and so on. These characteristics of gametophytic showed that it was a middle type on phylogeny and evolution. Many young sporophytes were obtained by artificial culture of spores, which established foundation for protective development and utilization of resource of L.japonicum.

Key words: Lygodium japonicum(Thunb) Sw., gametophyte, morphological characteristic