1. The gametophyte generation of Pteris sulcata L. is ordinarily produced by the germination of a spore. 2. The embryo sporophyte is of apogamous origin. 3. The gametophyte generation of Pteris sulcata under certain conditions was produced aposporously. 4. The gametophytic portions or gametophytes were formed in connection with the lamina or the petiole of the primary leaf. In one instance a prothallium was produced from both lamina and petiole of the primary leaf. A sharp line of demarcation usually exists between the cells of the gametophyte and the sporophyte. 5. The prothallial portions developed antheridia, secondary prothallia, and in one instance a sporoptiyte-like outgrowth. 6. The antherozoids, produced by the aposporously developed prothallia, were actively motile and normal in appearance. 7. Occasionally forms intermediate in character between gametophyte and sporophyte were formed. 8. It seems probable that the origin of the aposporously produced gametophyte may be traced to an early stage in ...