The group 342 is characterized by a special type of ascocarp, the perithecium.
As at present limited, the Pyrenomycetes are "ascigerous fungi having the fructification enclosed within a perithecium."
A perithecium, or cell excavated in the stroma which fulfils the functions of a perithecium, is always present.
When fully mature, the asci are ruptured and the sporidia escape by a pore which occupies the apex of the perithecium.
The dissemination of the sporidia may, from identity of structure in the perithecium, be deemed to follow a like method in all.
Moeller, on the contrary, represents each body as a perithecium, and our examination confirms Moeller's view.
D, The same, beginning to be surrounded by the hyphae forming the perithecium wall.