Microstructural Observation on the Development of Gametophytes and Oogenesis in the Fern Stenoloma chusanum

The development of gametophytes and oogenesis in the fern Stenoloma chusanum were studied using microscopy technology.Results showed that:(1)The spores are brown,monolete,surface smooth or verrucous grain;spores germinate about 12 days after sowed.Spore germination type is Vittaria-type.Prothallus development type is Adiantum-type.(2)Section observations showed that the archegonium of the S.chusanumdevelops from a superficial cell called initial cell.The initial cell forms a tier of three cells by two divisions.The upper cell develops into an elongated neck.The middle cell,called primary cell,finally develops into a neck canal cell,a ventral cell and an egg by two unequal divisions.When new formed the periphery of the three cells is appressed closely to the jacket cells of the archegonium.During maturation,a separation cavity occurs between the egg and the ventral canal cell,from periphery to the middle.Then,the neck canal cell and the ventral canal cell began to degenerate.Separation cavity expanded toward the middle,until a pore structure,called fertilization pore,occurred.In the later stage of oogenesis,on the upper surface of the egg,an egg envelope forms,and the neck canal cell and the ventral cell degenerate into a mass of amorphous materials.This study elaborated in details the morphological characteristics of gametophytes and oogenesis in the fern S.chusanum,and has scientific significance in illustrating the archegonium development features and revealing the mechanism of sexual reproduction.