Description: Thallus crustose, thinly episubstratic, continuous, slightly cracked or rarely warted-areolate, mostly finely granulose, pale grey to greenish grey. Apothecia lecideine, 0.6-1.5(-3) mm across, sessile and constricted at base, pale pink, with a flat to finally convex, epruinose or slightly pruinose disc, and thin, usually paler, finally sometimes excluded proper margin. Proper exciple colourless, 50-70 μm wide laterally, with evenly dispersed, very small, reddish crystals soluble in K, especially in upper part, the outer rim with a single layer of enlarged cells (to 9 x 6 μm); epithecium colourless, inspersed with small crystals between the apices of paraphyses; hymenium colourless, 75-85 μm high; paraphyses 0.8-1.2 μm thick at mid-level, the apical cells more or less clavate, to 3 μm wide; hypothecium colourless or very pale yellow. Asci 8-spored, cylindrical-clavate, surrounded by a gelatinous I+ blue coat, with a well-developed I+ blue tholus, an I+ darker blue tube and a well-developed ocular chamber, Bacidia-type. Ascospores (3-)5-15-septate, hyaline, acicular, curved or sigmoid, (40-)60-100 x (2.5-)3-4(-5) μm. Pycnidia colourless, half-immersed. Conidia 5-9-septate, hyaline, thread-like, slightly curved, 10-17 x 0.5-0.8 μm. Photobiont chlorococcoid, the cells 5-12 μm in diam. Spot tests: thallus and apothecia K-, C-, KC-, P-, UV-. Chemistry: no lichen substances.
Note: a mild-temperate to Mediterranean-Atlantic lichen found on deciduous trees (especially Acer and Fraxinus, but also on Quercus ilex) in humid, open forests and in woodlands along rivers, declining and perhaps extinct in northern Italy, but still locally abundant in suitable habitats of southern Italy. The species is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)