Arthonia granitophila Th. Fr.

Bot. Notiser: 39, 1865.
Synonyms: Melaspilea granitophila (Th. Fr.) Coppins; Melaspilea subarenacea J. Nowak & Kiszka
Description: Thallus crustose, poorly developed, consisting of grey, brownish or rusty orange granules scattered around the apothecia. Apothecia black, epruinose, adnate to sessile, round to short-ellipsoid, up to 0.4 mm wide, with a concave to flat disc and a poorly evident proper margin. Proper exciple black, carbonized, extending below the hymenium; epithecium brown-black, granulose, K-; hymenium colourless to pale brown, 40-50 µm high, I+ blue; paraphysoids branched and anastomosing, thread-like, the apical cells not markedly swollen; hypothecium dark brown to brown-black, continuous with the exciple, up to 40 µm high. Asci 8-spored, clavate to pyriform, semi-fissitunicate, with an internal apical beak. Ascospores 1-septate, with subequal cells, at first hyaline then pale brown and warted, ovoid-oblong to sole-shaped, 10-15(-17) x 4-6 µm. Photobiont trentepohlioid. Spot tests: K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: on steeply inclined to underhanging surfaces of acid siliceous rocks, with optimum in the montane and subalpine belts. Not reported from Italy, but known from several localities in the Eastern Alps (Austria), including Carinthia and Tyrol. To be looked for in the Italian Alps.
Growth form: Crustose
Substrata: rocks
Photobiont: Trentepohlia
Reproductive strategy: mainly sexual

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Predictive model