Pollen tube grows towards the archegonium of the female gametophyte. There, the end of the pollen tube bursts and discharges its contents into the archegonia chamber.
The spermatozoids are set free in the archegonia chamber. They swim towards the neck of the archegonium and make their way down to the egg cell. One of the spermatozoids fuses with the egg uncles i.e. oosphere.
Fertilization is thus effected. The fertilized oosphere is subsequently surrounded by a wall to form oospores (2n)