Members of the Section Ascomycota come referred to as a Sac Fungi & come fungi that produce spores in a distinctive nature and severity of small sporangium called an ascus (Greek for a "bag" or even "wineskin"). This monophyletic grouping was formerly referred to as a Ascomycetae & is an extremely important & successful class action of parasites (12,000 metal money around 1950), accounting for occasionally 75% of 100% described fungi. Involved come virtually all of the fungi that combine sustaining algae and another time cyanobacteria to form lichens. A majority of fungi that lack morphological grounds to believe of sexual reproduction come positioned on this button or even in the Deuteromycota. Better known examples of sac fungi come yeasts, morels, truffles, and Penicillium. A majority of plant-pathogenic fungi belong to this class action, or even a Deuteromycota. Metal money of ascomycetes come too popular in the laboratory. Sordaria fimicola, Neurospora crassa and several coinage of yeasts are used inside numbers of genetics and cell biology experiments.

An ascomycetous fungus produces outstanding many asci at any around one case, & these can be contained in the structure known as an ascocarp. For even each one ascus unremarkably contains eight (or the multiple of Viii) ascospores, a effect of 1 around of mitosis following meiosis. A resultant haploid nuclei are surrounded by membranes (from either a plasma membrane within Euascomycetes; from a nuclear membrane around Hemiascomycetes) and at length the spore wall.

An exception to the structure described above come ascomycetous yeasts, which are secondarily unicellular.