Abstract: The development of gametophytes and oogenesis of the fern Pteridium aquilinum var. latiusculum was studied using microscopical techniques. The spores are brown, tetrahedral and trilete. The spores germinate about 3-7 days after being sowed. They develop into prothallia through filament and plate stages. The adult prothallia are usually dioecious or hermaphroditic. Section observations show that the archegonium of the P.aquilinum var. latiusculum develops from a superficial cell, i.e. the initial cell of archegonium, which forms a tier of three cells by two divisions. The upper and lower cells develop into the jacket cells of the archegonium. The middle cell, i.e. the primary cell,finally develops into an egg, a ventral canal cell and a neck canal cell by two unequal divisions. When new formed, the periphery of the three cells is appressed closely to the jacket cells of the archegonium. A large amount of vesicles are seen in the cytoplasm. During maturation, a separation cavity occurs between the egg and the ventral canal cell, but a pore region persistently connects the two cells. Simultaneously, the egg membrane is formed in the upper surface of the egg. Thereafter, the neck canal cell and ventral canal cell degenerate gradually. Some black granular substances appear in the jacket cells of archegonium. Series sections show that a fertilization pore appears in the central region of the upper surface of the mature egg. The ultrastructural observations are needed to elucidate the detailed cytological features of oogenesis.

Key words: Fern, Pteridium aquilinum var. latiusculum, Oogenesis, fertilization pore