Mucor, Exoasci, Ustilagineae, higher Ascomycetes and Basidiomycetes); and (2) the question as to the physiological nature and meaning of fermentation.
The Ascomycetes, Rust Fungi, &c., the same structure obtains so far as all essential details are concerned.
In 1865 De Bary suggested the possibility that such lichens as Collema, Ephebe, &c., arose as a result of the attack of parasitic Ascomycetes upon the algae, Nostoc, Chroococcus, &c. In 1867 the observations of Famintzin and Baranetzky showed that the gonidia, in certain cases, were able to live outside the lichen-thallus, and in the case of Physcia, Evernia and Cladonia were able to form zoospores.
Contrary to the behaviour of the non-lichen forming Ascomycetes the lichen-fungi show very few cases of ordinary conidial formation.
We find two chief types of fruit bodies in the lichens, the perithecium and apothecium; the first when the fungal element is a member of the Pyrenomycetes division of the Ascomycetes, the second when the fungus belongs to the Discomycetes division.