Physcia adscendens H. Olivier forme corticole.
Thallus foliose, loosely appressed to the substratum, to 5 cm across (when confluent with other colonies), lobes 0.5-1 mm wide, apices up-turned, bent and swollen, hood or helmet-shaped, (usually lighter than the thallus which makes them visible from afar), containing cream to pale yellow soredia (NB these caps or helmets are fragile and can, when breaking, leave only a section of the tube containing soredia); lobe margins bearing long marginal cilia (0.5-2 mm) with dark tips, upper surface whitish, pale grey when dry, grey-greenish when moist, without pruine, dotted with numerous whitish pseudocyphella, lower surface whitish with rhizines, tips blackish. Seldom fertile and with rare apothecia, 1-2 mm diam., shortly stalked, disc concave, brownish to blackish, pruinose, exciple thick, prominent. Ascospores brownish to blackish, 1-septate, sometimes with a polarilocular aspect, 16-23 x 7-10 µm according to literature, 14-20 x 6-9 µm according to our measures. Pycnidia sometimes abundant and visible as black dots. Cortex K+ yellow; medulla: K-. Very variable species, not especially maritime, frequent on the bark of trees (even in cities because quite tolerant to pollution) also abundant on various substrates (even artificial) see the following forms:
Physcia adscendens forme saxicole: on low acid rocks rich in organic matter, particularly by the sea.
Physcia adscendens forme sur ciment ou sur béton: on cement or concrete.
Physcia adscendens forme foliicole: tiny form occurring on evergreen leaves, especially Buxus.
Physcia adscendens forme lignicole: rare form forming pads on dead or worked wood.
Physcia adscendens forme maritime: darker greyish, form occurring in the mesic or xeric zone and subjected to seawater projections.
Physcia adscendens forme sur substrats artificiels: form coming on artificial plastic substrates (boat hulls, etc.).
See also Physcia tenella very close and often difficult to separate but at the ends of the lobes not in hood and whose soredia are labriforms (This last species is sometimes considered identical by some authors because there are many intermediates and even chimeras). See also Physcia leptalea which is not sorediate and which can come in mixture.