There are three methods of reproduction of the lichen: by fragmentation, by soredia, by the formation of fungal spores.
The soredia are found in a large number of lichens, and consist of a single gonidium or groups of gonidia, surrounded by a sheath and hyphae.
The soredia are the most successful method of reproduction in lichens, for not only are some forms nearly always without spore-formation and in others the spores laregly abortive, but in all cases the spore represents only the fungal component of the thallus, and its success in the development of a new lichen-thallus depends on the chance meeting, at the time of germination, with the appropriate algal component.
Xylographa, e, f, Two soredia in the act of germinating; the Graphis, &c.) or hyphal envelope has grown out below into G none (e.g.
In the majority of forms it is clear that the soredia rather than the ascospore must play.