Parmelia saxatilis  

Thallus foliose, 3-6 (-20) cm diam., often forming complete or partial rosettes, ± loosely attached. Lobes to 3 mm wide, slightly broadened and truncate at the apices, discrete, or contiguous and overlapping. Upper surface grey-white to grey-green, sometimes tinged brownish towards the lobe ends or if stored for many years, with oval to elongate, ± raised, scattered, white pseudocyphellae which may fuse to form a ± complete, coarse, network. Isidia concolorous or with brown-tinged tips, cylindrical, simple, becoming coralloid, at first arising from pseudocyphellae, later from the rest of upper surface, rather sparse or becoming numerous and obscuring the thallus. Lower surface black, brownish towards the margin. Rhizines dense, simple, occasionally forked.
Anamorph: conidiomata pycnidia. Conidia 6-7 × ca 1 μm, cylindrical or bacilliform.
Teleomorph: ascomata apothecia, occasional, to 1 cm diam, sessile or shortly stalked. Disc red-brown to dark brown. Thalline exciple often isidiate. Ascospores 16-18 × 9-11 μm, ellipsoidal to ovoid, aseptate, thick-walled, smooth.
Chemistry: cortex K+ yellow; medulla C–, K+ orange, KC+ orange, Pd+ orange, UV– (atranorin, salazinic, ± lobaric and ± norstictic acids).