ascospore

An ascospore is a sexually produced spore formed within a saclike structure called an ascus. Asci are produced by fungi belonging to the phylum Ascomycota, also known as sac fungi. Typically, four or eight ascospores develop within a single ascus.1

These asci can form directly from the fungal mycelium or within a fruiting structure called an ascocarp. In some cases, like with yeasts, a single cell transforms into an ascus. While lichen fungi produce numerous spores, including ascospores, it's suggested that these spores may not always be functional for propagating the lichen association itself, as free-living algae capable of forming new associations are not always readily available. However, some lichens have mechanisms where algae are discharged with the spores, allowing for new lichen formation upon germination.12