Physcia stellaris (L.) Nyl.
Thallus foliose, more or less rosette-shaped, 2-4 cm diam., lobes closely appressed around branches (as hand fingers grasping a branch), more or less separate and radiating, upper surface not pruinose, not tomentose nor flecked or spotted (at least when dry, although relative), very pale grey, whitish, sometimes with a green-bluish tinge, lower surface pale grey-brownish with simple or branched rhizines. Apothecia in limited number, 2-3 mm diam., sessile or shortly-stalked, disc grey-bluish, dark blue, brown-black, brown-greyish, slightly pruinose, exciple thick, concolourous to the thallus. Ascospores 1-septate, 15-22 x 7-11 µm. Pycnidia frequent, black. Cortex : K+ yellow , medulla K- (in the field, scratch the cortex to expose the medulla before using K). Thermophile, rare in our prospection area (or mistaken), easily confused with Physcia aipolia much more frequent, larger, with lobes markedly flecked (even when dry) and with a K+ yellow medulla.*