anisogamic gametangiogamy (noun,no plural) – the fusion of two structurally different gametangia, one male gametangium called antheridium and one female gametangium called archaegonium, or, more accurately, ascogonium (i. e., the archaegonium of ascomycetes). Both gametangia contain either a single haploid nucleus or they have several haploid nuclei. The male nucleus (or several nuclei) from the antheridium are typically released into the cytoplasm of the ascogonium through a projecting hyphae called the trichogyne, directly at the contact point of both gametangia. Asci are then formed from ascogeneous hyphae that directly grow out of the ascogonium. In a variation of this process single sex cells (sperm cells) can be formed from the antheridium. During this process called spermatogamy, not the entire antheridium fuses with the trichogyne, but only the single male gametes, the conidia-like sperm cells.