The gametophyte generation of a fern is when a spore from a fern is germinated to form a haploid cell. The gametophyte generation begins when spores are transferred to suitable locations and begin to germinate. It ends when the spore grows into a prothallus.
A prothallus is a germinated fern spore that contains rhizoids to absorb water and nutrients from the soil, archegonia to produce an egg or antheridia to produce a sperm. The prothallus may also contain both archegonia and antheridia. If the soil contains a lot of moisture, then fern sperm can come in contact with the egg of a fern. Fertilization occurs, and the sporphyte generation begins as the fern starts to grow into a plant.