Physcia tribacioides Nyl.
Thallus foliose, irregular, elongate or rosette-shaped, 3-8 cm across, composed of lobes, tightly appressed to the substratum, 0.5-1.5 mm wide, margin indented or more or less crenulate, upper surface not distinctly white flecked, grey-whitish, pale grey-greenish when dry, green when moist, covered with soralia, mostly marginal, farinose, globose, 0.5-1.5 mm diam., whitish when dry (never bluish), white-yellowish when moist, underside pale brown, simple whitish to brown rhizines. Apothecia very rare, sessile, 1-1.5 mm diam., disc brown-reddish, not pruinose, thalline exciple, distinct, concolourous to the thallus. Ascospores brownish, more or less polarilocular, 17-22 x 7-10 µm. Photobiont: Trebouxioid. Cortex and medulla : C-, K+ yellow, Pd-. Thermophile, maritime and oceanic trends, on bark of tree trunks, isolated or in aalignment near the sea. N.B. Ths species seems to be expanding owing to the global warming.*