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.
Nostoc lichenoides in most of rutida in Omphalaria; Lichina, in Peltigera, Pannaria and Stictina; Gloeocapsa polydermatica in Baeomyces and Omphalaria; Sirosiphon pulvinatus in Ephebe pubescens.
In the case of Solorina, for example, the principal alga is a green alga, one of the Palmellaceae, but Nostoc (a blue-green alga) is also found playing a subsidiary part as FIG.
- Section of Homoiomerous Thallus of Collema conglomeratum, with Nostoc threads scattered among the hyphae.
(Cystococcus, Nag.) C, Nostoc from the thallus of Physma attacked by the germ-tube from a chalazanum.