Description: Thallus crustose, thinly episubstratic, smooth-areolate to slightly warted, pale to bluish grey, covered in irregular, sorediate patches that can finally occupy almost the entire surface, giving the thallus a subleprose appearance. Soredia granular, yellowish to pale yellow-green, c. 15-30 μm. Apothecia unknown. Pycnidia black, matt, 80-225 μm across in surface view, mainly isolated in non-sorediate areas, semi-immersed, projecting with the upper half to one quarter, depressed-globose, the ostiole circular, c. 20 μm wide, often appearing as a whitish-cream spot. Pycnidial wall dark brown, of 2-3 layers of intertwined, thick-walled, brown to dark brown hyphae, K+ purplish, the hyphae irregular in thickness, mainly 3-6(-7) μm thick, short-celled, smooth, immersed in a gel, friable and readily disintegrating on sectioning. Paraphyses packing the conidiomatal cavity, ± vertically oriented, hyaline, aseptate, filiform to snake-like, sparsely branched, some with arcuate apices, densely intertwined, (30-)50-75(-80 or more) μm long, 0.5-1.5(-2) μm thick; conidiogenous cells elongate-cylindrical. Conidia arising singly, not forming chains, narrowly ellipsoid, hyaline, aseptate, 3-5 x 1.5-2 μm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow to yellowish brown, C-, KC-, P-. Chemistry: atranorin, 2’-O-methylperlatolic acid (or a similar substance).
Note: a rare, but easily overlooked species found on bark of deciduous trees in areas with a humid climate, with very few stations in the Alps outside Italian territory (Austria, Switzerland). To be looked for in Italy.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)