A cardinal organ part (PO:0025001) that is the enlarged basal part of an archegonium (PO:0025126) and has an archegonium egg cell (PO:0025122) located in it. [source: ISBN:0962073342]
Comment
After fertilization, the venter develops into the spore capsule calyptra (PO:0030037), which protects the sporangium (syn: spore capsule; PO:0025094) containing the developing sporophyte.