The development of gametophyte and oogenesis of the fern Coniogramme emeiensis Ching et Shing are studied by light microscopy (LM) and transmission electron microscopy (TEM).The spores germinate about 7 days after sowed.They develop into cordate prothallus through filament and plate stages.The adult prothallia,usually hermaphroditic,produce antheridia in the basal and archegonia near the apical notch of the prothallus.Studies on the oogenesis show that the archegonium of the C.emeiensis develops from a superficial cell,i.e.the initial cell of archegonium.The initial cell forms a tier of three cells by two divisions.The middle cell,i.e.the primary cell,finally develops into a neck canal cell,a ventral canal cell and an egg by two unequal divisions.Plasmodesmata connect the egg and the ventral canal cell when the egg is newly formed.During maturation,a separation cavity forms around the egg,but plasmodesmata still connect the egg and the ventral canal cell in the pore region.In the mid stage of oogenesis,the nucleus produces extensive evaginations.In the later stage of oogenesis,an egg envelop forms around the egg,the absence of egg envelope from the pore region,where the egg and ventral canal cell were formerly interconnected,produces a fertilization pore.At this stage,the numbers of the evaginations are reduced.This study elaborated the whole processes of gametophyte development,archegomium formation and oogenesis in C.emeiensis,which have some science significance to reveal the evolutionary relationship of Hemionitidaceae in the ferns.