General:
Common Names: The Icelandmoss Lichens (and others). Several are assigned to this genus, reflecting its very heterogeneous circumscription: “Brown” is applied to two species (C. commixta and C. hepatizon), stressing their surface colour and, more importantly, their generic similarity with other lichens of that name (i.e., members of Melanelia and Neofuscelia). “Icelandmoss” is the traditional name given to Cetraria islandica and its allies. “Paperdoll” is a fanciful name applied to two species (C. cucullata and C. nivalis), referring to their pale, upright, “cut-out” lobes. “Ruffle” is applied to several species, describing their typically wrinkled upper surface. “Thornbush” is applied to two species (C. californica and C. merrillii), conveying their spiny, shrub-like habit.
Small to large stratified foliose lichens, corticate above and below, sorediate or not, lobes rather closely appressed to semi-erect or erect, short to more often elongate, averaging to 0.5–10 (–12) mm wide, thin to somewhat thick, occasionally bearing protruberant marginal pycnidia or cilia. Upper surface brownish, blackish, or brightly coloured; lower surface coloured alike with upper surface, often lacking rhizines. Medulla white (rarely yellow). Photobiont green.
Apothecia located along lobe margins, disc brown or black; spores simple, spherical or ellipsoid, colourless, 8 per ascus.
Notes: Thirty-eight species of Cetraria are reported for North America. Nineteen of these occur in B.C. As presently delimited, Cetraria is a heterogeneous genus. Although several species groups are segregated from it as distinct genera (e.g. Asahinea, Cetrelia, Esslingeriana, Masonhalea, Platismatia and Vulpicida), a number of other species and species groups also deserve generic rank. Recently Hale (1987) transfered some of these to Tuckermannopsis. This disposition, however, seems more nomenclatural than taxonomic and is not followed here. Also not accepted here (pending further study) is the separate genus Allocetraria (Randlane and Saag 1992).

Species description:
Upper surface essentially dark: olive-green, brown or blackish AND
Soredia absent; true isidia also absent AND
Growing directly over rock AND
Thallus more delicate, usually readily cut; lobes more broadly attached to substrate; rhizines present; distribution various AND
Pseudocyphellae and pycnidia usually restricted to lobe margins, pycnidia erect and cylindrical; medulla thin; rhizines located only along lobe margins AND
Lobes usually rather short; lobe margins not distinctly rimmed; lower surface pale; pseudocyphellae strictly marginal (i.e., positioned at right angles to upper surface); medulla KC+ reddish or KC-

Comments:
Cetraria commixta is said to havea pale lower surface, whereas in the related C. hepatizon the lower surface is black. In the B.C. material, however, these characters are variable.

Reactions:
Cortex KC+ yellowish.

Contents:
Protolichesterinic and usnic acids.

Source:  Lichens of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration By:  Trevor Goward