Anarchegonium (pl.:archegonia), from theAncient Greekἀρχή ("beginning") andγόνος ("offspring"), is a multicellular structure or organ of thegametophyte phase of certainplants, producing and containing theovum or femalegamete. The corresponding male organ is called theantheridium. The archegonium has a long neck canal or venter and a swollen base. Archegonia are typically located on the surface of the plantthallus, although in thehornworts they are embedded.
Inbryophytes and othercryptogams,sperm reach the archegonium by swimming in water films, whereas inPinophyta andangiosperms, thepollen are delivered by wind or animal vectors and the sperm are delivered by means of apollen tube.[citation needed]
In themossPhyscomitrella patens, archegonia are not embedded but are located on top of the leafygametophore (s. Figure). ThePolycomb protein FIE is expressed in the unfertilizedegg cell (right) as the blue colour afterGUS staining reveals. Soon afterfertilisation, theFIE gene is inactivated (the blue colour is no longer visible, left) in the young embryo.[1][2]
They are much-reduced and embedded in the megagametophytes ofgymnosperms. The term is not used forangiosperms or the gnetophytesGnetum andWelwitschia because the megagametophyte is reduced to just a few cells, one of which differentiates into the egg cell. The function of surrounding the gamete is assumed in large part bydiploid cells of themegasporangium (nucellus) inside theovule.Gymnosperms have their archegonium formed afterpollination inside femaleconifer cones (megastrobili).[3]
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