Abstract: The development of gametophytes of Osmunda cinnamomea L.var. asiatica Fernald was studied. The spore is tetrahedral(47.4×44.3μm.), trilete, and ellipsoidal in equatorial view,subspheroidal in polar view, with various short club shaped ornamentations. The pattern of spore germination is of centrifugal type (Momose 1942) or polar germination (Nayar 1971). In the cultures on the north windowsill late in spring and summer the majority of the spores germinate into a two-celled filament with a chloroplast-containing rhizoid. The wedge-shaped apical cell may appear in 4 days. These are similar to O. cinnamomea L. described by Stokey et al. (1956). However the spores germinate into quadrantal-shaped masses at 2000 Lux. and 20℃. The mode of development in this variety seems similar to that of O. regalis L. described by same authors.The prothallial development is of the Osmunda type (nayar 1971). The adult prothalli are naked and typically cordate, broad rounded-obovate, broad obovate or broad lanceolate, and length longer than width (often 2×1.5). When the sex organs appear, the midrib is about in 6-7 celled thick, obovate,ovate or elongate obovate. The antheridia appear in 6-8 weeks, and the archegonia 4 weeks later.The antheridia develop on the margin or ventral surface of the prothallus. They are of large primitive type with 7-8 celled wall. The operculum is discharged at dehis-cence. Each antheridium contains about 48-51 spermatozoids 28 flagellated. The archegonia develop along the side of the midrib. Only 6 archegonia arranged regularly in 3 couples on the both opposite sides of the midrib have been found. Its neck is 6 celled-high. tapers toward the tip and extends straight from the prothallus. In the present work, The germination of the spore in this variety shows different characteristics under different conditions, as mentioned above. They are either similar to O. cinna-momea L. under insufficient light or to O. Tegalis L. under full illumination. This implies that this variety may have rather broad adaptations to the varying environments.