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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.
Over soil, moss or occasionally base-rich rock; lower surface pale, sometimes cottony; fruiting bodies (apothecia) not immersed, usually hemispherical at maturityAND
Apothecia black, situated primarily along lobe margins (check young apothecia); lobes closely appressed throughout; upper surface sometimes bright red AND
Lobes larger, averaging to more than 2.5 mm wide at maturity, upper surface variously coloured, smooth to fissured; spores 1-celled AND
Upper surface bright red to brownish red, usually not heavily white-pruinose, smooth to occasionally fissured; widespread
All spot tests negative.
Source: Lichens of British Columbia