The lichen genera Arctocetraria, Cetraria and Cetrariella (Parmeliaceae) and their presumed evolutionary affinities.
A circumscription of the lichen genus Cetraria Ach. s.s., presently comprising 15 species, is made. The genus is characterized by oblong, citriform conidia as well as characters of the ascus: a small axial body and a distinct amyloid ring structure in the tholus (the region between the ocular chamber and the outer membranes in the apex of the ascus). All fertile species of Coelocaulon Link are inc
