The article deals with the effect of sowing density of spores on ontogenesis of gametophytes Matteuccia struthi-opteris (L.) Tod. This species is included in the Red Data Book of the Kursk Region (Krasnaia…, 2017). The ability to form viable gametophytes from spores in Matteuccia struthiopteris is often reduced and depends on many factors, including the population density of the seedlings themselves. Among the numerous forms of thalli of gametophytes in M. struthiopteris (filamentous, spatulate, asymmetric, cordate, wide-heart), only wide-heart thalli form an archegonial cushion capable of fertilization and formation of a zygote with further development of sporophyte. Under natural conditions, the presence of young sporophytes is an important factor contributing to the rejuvenation of populations of M. struthiopteris and an increase in their vitality. In the course of the study, it was established how significant the mutual influence of gametophytes is for their development.