antheridium The male sex organ or gametangium, within which male gametes are formed, in algae, fungi, bryophytes (mosses, liverworts, etc), and pteridophytes (ferns).

antheridium (pl. antheridia) The male sex organ of algae, fungi, bryophytes, clubmosses, horsetails, and ferns. It produces the male gametes (antherozoids). It may consist of a single cell or it may have a wall that is made up of one or several layers forming a sterile jacket around the developing gametes. Compare archegonium.