Pyrenomycetes

Largest group of fungi (see fungus) in the class Ascomycetes, containing about 640 genera and 6,000 species. Most are small and inconspicuous, but a few are larger. They are characterized by flask-shaped fruiting bodies that release their spores either by opening at the top or by decaying. Some species are parasitic on plants, others on insect larvae, and some are saprophytes. Claviceps purpurea is the cause of the ergot disease of rye; Cordyceps attacks certain caterpillars; Eurotium aspergillus is the greenish mould which attacks jam.