An order of ascomycetous fungi of parasitic or saprophytic habit, with the tissues usually hard and somewhat coriaceous.
The Century Dictionary (Public Domain)
Use "pyrenomycetes" in a sentence
"Those which vegetate most luxuriantly there are the _fungi_, and among them especially the _pyrenomycetes_, which are frequent in the waters of mines."
"Gnomoniopsis are leaf and stem inhabiting pyrenomycetes that infect plants."