Gametophytes of the Ophioglossaceae are tuberous, nonchlorophyllous, nonphotosynthetic, and subterranean. They are parasitic on mycorrhizal fungi which invade their tissues. It is difficult to study these gametophytes in their underground habitat because they are rarely found. Recent work has been done in axenic culture because it offers the opportunity to investigate their development and reproduction for extended periods of time. Depending on the species, the spores germinate after two weeks to several months in the dark. Usually, germination is inhibited by nitrate and promoted by ammonium. The gametophytes remain in the 4-5 celled stage in culture if sugar is not available. Sugar replaces the need for a fungus under these conditions. Normal gametophyte morphology occurs in culture on a nutrient medium containing minerals, including ammonium, and sugar without the fungus. Mature gametophytes of this family can be cylindrical, spherical, tongue-shaped, or bean-shaped and they develop antheridia before becoming bisexual. The gametangia are adjacent to each other which may contribute to the inbreeding known for Botrychium. Although gametopyhtes of some species may mature in less than a year after spores are released in nature or sown in culture, it has been reported that other species may take 20 years to form embryos. In culture, the fastest gametophyte maturation is about 8 months with Ophioglossum crotalophoroides. Normal embryo development produces a root that emerges from the gametophyte prior to the first leaf. In axenic culture, young sporophytes of Botrychium jenmanii can form one root and three leaves 15 months after the spores were sown. However, after fertilization in some species, a delay in the emergence of a leaf above the soil of 5 or more years can occur because several roots or rudimentary leaves are formed by the young sporophytes.

Key words: development, ferns, gametophyte, Ophioglossaeae