Physcia biziana (A. Massal.) Zahlbr. var. biziana

        Thallus foliose, rosette shaped, 5-10 cm diam., lobate,lobes adjoining, 2-3 mm long, little overlapping, folded, except at their tips, not bent, upper surface pruinose, dull whitish when dry, greenish when moist (or turning green when sprayed with water - rather specific trait), lower surface dull whitish to pale brown, rhizines simple, pale to whitish. Apothecia usually numerous, more or less clustered towards the center, cup-shaped, sessile, 1-1.25 mm diam., disc concave to flat, pruinose to powdery, grey, grey-brown, grey-blue, grey-purple, exciple concolourous, smooth to convoluted. Ascii 60-70 x 20-25 µm according to our measures. Ascopores broadly ellipsoid, slate brown, 1-septate, 13-20 x 7-12 µm according to literature, 16-20 x 7-10 according to our measures. Photobiont: chlorococcoid. Cortex : C-, K+ yellow, KC+ yellow, Pd- ; medulla: C-, K-, KC-, Pd-. Thermophile, mediterranean, on bark of isolated trees or ornmental trees.

Cf.: Physcia stellaris  of which the thallus is smaller, not turning greenish when moisten, and Physcia aipolia with an upper surface dotted with pseudocyphellae and medulla K+ yellow.

_ Here is, particularly in Corsica, a form occurring on the dead wood of Juniperus and more rarely on Pinus, see: Physcia biziana forme lignicole.