Archegonium
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Image:Archegonium.jpg An archegonium (pl: archegonia), from the ancient Greek αρχη (beginning) and γονος (offspring), is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. The archegonium has a long neck and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the horned liverworts they are embedded.
They are also much-reduced and embedded in the megasporangium of gymnosperms. The term is not used for angiosperms or the gnetophytes Gnetum and Welwitschia because the comparable "structure" is reduced to just a few cells, and the function of surrounding the gamete is completely assumed by diploid cells of the megasporangium.
The corresponding male organ is called the antheridium.de:Archegonium