Archegonium
An archegonium, from the Ancient Greek ἀρχή and γόνος, is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female gamete. The corresponding male organ is called the antheridium. The archegonium has a long neck canal or venter and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the hornworts they are embedded.
Bryophytes
In bryophytes and other cryptogams, sperm reach the archegonium by swimming in water films, whereas in Pinophyta and angiosperms, the pollen are delivered by wind or animal vectors and the sperm are delivered by means of a pollen tube.In the moss Physcomitrella patens, archegonia are not embedded but are located on top of the leafy gametophore. The Polycomb protein FIE is expressed in the unfertilized egg cell as the blue colour after GUS staining reveals. Soon after fertilisation, the FIE gene is inactivated in the young embryo.