Publisher: AMER BRYOLOGICAL LICHENOLOGICAL SOCIETY INC
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 incorporated into Cetraria, based upon the similarities in ascus structures and conidia. Two new combinations are made: Cetraria crespoae (Barreno & Vázquez) Kärnef. and C. steppae (Sav.) Kärnef. Two new genera, Arctocetraria Kärnef & Thell and Cetrariella Kärnef. & Thell are described, each of which differs in ascus structure from Cetraria. The new combinations Arctocetraria andrejevii (Oxn.) Kärnef. & Thell, A. nigricascens (Nyl. in Kihim.) Kärnef. & Thell, Cetrariella delisei (Schaer.) Kärnef. & Thell, and C. fastigiata (Nyl.) Kärnef. & Thell are made. Two additional species, earlier presumed to belong to Cetraria in the rather strict sense, are transferred to Tuckermannopsis Gyeln., mainly because of similarities in the ascus structure; the new combinations Tuckermannopsis inermis (Nyl.) Kärnef. and T. subalpina (Imsh.) Kärnef. are made to reflect this change. The presumed evolutionary affinities of all of these taxa are discussed.