Squamules: up to 4 mm wide, elongate, imbricate, weakly concave to weakly convex; upper surface: reddish brown or medium brown to dark brown, dull, epruinose or partly pruinose, smooth or sparingly fissured; margin: white, straight, lobed; upper cortex: up to 80-160 μm thick, composed of thick-walled hyphae with angular lumina, not containing crystals of lichen substances, sometimes containing calcium oxalate; medulla: not containing lichen substances, sometimes containing calcium oxalate; lower cortex: poorly developed, of anticlinally oriented hyphae, containing calcium oxalate; lower surface: white to medium brown, K-; Apothecia: up to 2 mm diam., laminal, immarginate even when young, black or dark brown, epruinose or white or yellow pruinose. ascospores: 11-14 x 7-9 μm; Pycnidia: laminal, immersed; conidia: bacilliform, 6-7 x 1 μm; Spot tests: upper cortex and medulla K-, C-, KC-, P-; Secondary metabolites: none.
Psora himalayana differs from P. globifera mainly in having somewhat smaller, distinctly white-edged, and more regularly imbricate squamules containing calcium oxalate in the medulla and/or the lower cortex. Pruinose specimens of P. globifera sometimes resemble P. himalayana but may be distinguished morphologically by having the pruina mainly on the upper side near the margin of the squamules, not mainly along the margin. Psora himalayana is usually white on the lower side near the margin of the squamules, whereas P. globifera is usually pale to medium brown.
Some forms of P. tuckermanii with dark brown, small, distinctly white-edged squamules are distinguished by the usually paler apothecia and less distinctly imbricate squamules. There are, however, some specimens of P. tuckermanii with dark brown to black apothecia and small, white-edged squamules which may be difficult to identify. The upper cortex of P. himalayana is generally composed of more thick-walled hyphae with more angular lumina than that of P. tuckermanii. Crystals of calcium oxalate are deposited throughout the medulla or just below the algal layer in P. tuckermanii (sometimes absent), whereas the crystals occur mainly in the lower part of the medulla and/or in the lower cortex in P. himalayana.
Some terricolous specimens of P. himalayana with scattered, not imbricate squamules may resemble P. vallesiaca, and are most easily distinguished by the absence of norstictic acid.
Specimens with small, imbricate squamules are often named Psora elenkinii, see that species for discussion.
Central Asia and western North America.
Calciferous rock in open habitats, mainly in conifer forests and mountains.
Psora elenkinii, Psora globifera, Psora tuckermanii.