Description: Thallus leprose, cottony, whitish to pale grey, not sharply delimited, forming a soft, thick, more or less continuous, irregularly spreading crust, not lobed or obscurely lobed in young thalli, covered in up to 60 µm wide, coarse, soredia-like granules which are often clustered into up to 300 µm wide aggregates, with long (60-120 µm), conspicuous projecting hyphae which are visible with a hand-lense. Medulla absent or very poorly developed. Photobiont chlorococcoid, the cells up to 20 µm diam. Spot tests: K+ yellow, C , KC+ pale yellow, P- or P+ pale yellow, UV , or UV+ dull pink. Chemistry: atranorin and nephrosteranic acid.
Note: an ecologically wide-ranging species occurring on a wide variety of substrata (mainly acid bark, but also siliceous rocks, soil and mosses), both on rain-sheltered and rain-exposed sites, with optimum below the subalpine belt, certainly more common, also in the Alps, and to be looked for there.
Growth form: Leprose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)