A class in the phylum Ascomycota. The Loculoascomycetes form a well-developed mycelium which bears the sexual (ascus) and asexual (conidium) states, and are distinguished from other ascomycetes by their method of ascoma formation and their ascus structure. Ascoma formation is ascolocular, a type of development in which certain cells of the vegetative hyphae undergo numerous divisions to form a small mass of homogeneous tissue (stroma). As the stroma enlarges, internal differentiation occurs to form the ascogenous cells, from which the asci will form. As the asci develop, they dissolve or crush the internal tissues of the stroma (now an ascostroma), creating a cavity (locule). As the ascostroma matures, a neck with a canal for ascospore discharge usually forms. An ascostroma may have one or several locules with asci. Species with a single locule are termed pseudothecia, and they often resemble the perithecia of the Pyrenomycetes. The asci have a two-layered wall (bitunicate). The outer layer (ectotunica) is thin and rigid, whereas the inner layer (endotunica) is thicker and elastic. At maturity, the ectotunica splits, allowing the endotunica to expand and forcibly discharge the eight ascospores. The ascospores may be hyaline or brown, but they are usually multicelled.
Found primarily on living and dead plant tissues, the fungi in this class include a number of important plant disease fungi. See also Ascomycota; Eumycota; Fungi; Plant pathology.
