Description: Thallus crustose to subleprose, whitish to whitish grey, often somehow darker in the centre, usually well-delimited and sometimes obscurely lobed, entirly consisting in a compact mass of convex, rather firmly attached granules. The thallus starts developing as isolated, dispersed granules that form piles, or aggregations (best visible along the margins, where the dispersion of the young granules is most readily observed) which eventually overlap and become confluent, giving the false appearance of a continuous thallus in older areas. Granules 80-150(-200) μm in diam., sometimes grouped into larger, up to 300 μm wide aggregates, pseudocorticate, the surface compact, without projecting hyphae. Medulla greyish white, rarely exposed, the hyphae 2-5 μm thick, covered in places with small, colourless crystals. Photobiont chlorococcoid, the cells up to 17 μm wide. Spot tests: K- or K+ yellowish, C- or C+ reddish orange, KC+ reddish orange to orange-pink, P+ lemon yellow, UV-. Chemistry: alectorialic and roccellic/angardianic acids.
Note: a mainly arctic-alpine lichen found on moss cushions and stony siliceous ground on surfaces wetted by rain, mostly in snow-beds near or above treeline, reaching the nival belt in the Alps. Earlier records from Sardinia are dubious (Baruffo & al. 2006).
Growth form: Leprose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)