Abstract: The deyelopment of gametophytes of Adiantum pedatum L. was sas studied. The spore is tetrahedral, 28.93×42.57u, trilete and obtuse triangular in polar view, semiorbicular in equatorial view, with variously large or small lamellar flat ornamentations observed by scanning electron microscope. The pattern of spore germination is of centripetal type (Momose (1942). Generally the germ filaments develop 2-5 cells long, uniseriate, some-times to 7 cells long or multiseriate. The prothallial development is of the Adiantum type (Nayar 1971). The prothalli mature in 7-11 weeks after inoculum. They are naked and cordate, long obovate or broad obovata, length longer than width, about 5.5×4mm. The plants are strictly dioecious. The antheridia are long rounded globular, 50.68-55.1u in diameter. They always occur on the margin or surface of young prothalli. Its operculum is single. Each antheri-dium contaius about 30-31 spermatozoids, 30-49 flagellated.The archegonia develop on the midrib of matured prothalli.Its neck of is 5-6 celled high and reaches a length of 101.36-131.57u. Vegetative propagation is common in this species. The present work and another paper (Kachroo & Nayar 1953)show that the spore of genus Adiantum is tetrahedral and ger-mination pattern is centripetral, and its sex organs of that are rather large. It implies that these are common primitive char-ateristics of the genus. But the opereulum of antheridium of Adiantum pedatum is single, while the opcrculum of other speciesit divided (Kachroo & Nayar 1953). If single operculm isan advanced charater, Adiantum pedatum might be higher evolutionary level in this genus.