E-Flora BC: Electronic Atlas of the Flora of British Columbia

General:
Common Name: The Scale Lichens. Suggested by the tiny, rounded, often somewhat overlapping lobes of the species.
Small stratified squamulose lichens, corticate above, corticate or not below, nonsorediate, nonisidiate, squamules broadly attached to substrate or more often attached at one margin, closely appressed to loosely attached, short to more often subrotund, averaging to 2–5 (–8) mm wide, usually rather thick. Upper surface pinkish or more often brownish, somewhat shiny or not, often white-pruinose. Lower surface pale or darkening, lacking rhizines. Medulla white. Photobiont green.
Apothecia located over upper surface or along squamule margins, disc usually convex or hemispherical when mature, reddish brown to black; spores simple, ellipsoid, colourless, 8 per ascus.
Over exposed, base-rich soil or rock.
Notes: Psora is primarily a genus of semi-arid or arid areas, especially at temperate latitudes. Of the 17 species reported for North America, seven are found in B.C. This is a taxonomically difficult genus in which the species are not always clearly circumscribed.

Species description:
Over soil, moss or occasionally base-rich rock; lower surface pale, sometimes cottony; fruiting bodies (apothecia) not immersed, usually hemispherical at maturityAND
Apothecia reddish brown, brown or black, situated primarily over upper surface of lobes (check young apothecia); lobes appressed or ascending; upper surface never bright red AND
Lobes appressed or at most weakly raised, not distinctly ascending; upper surface brownish; apothecia simple, black to reddish brown AND
Apothecia dark brown to black; upper surface generally dark brownish AND
Lobes distinctly white-pruinose along margins; lower surface white in the vicinity of the margins

Comments:
Sterile material can be difficult to separate from nonfruiting specimens of Acarospora glaucocarpa. In Psora the algal layer is continuous, whereas in A. glaucocarpa the algae are organized in discrete clumps.

Reactions:
All spot tests negative.

Contents:
No lichen substances reported.