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, >80 μm wide laterally, of narrow, not distinctly radiating cell lumina with gelatinized walls which are thicker than the lumina, with evenly dispersed, very small, reddish crystals soluble in K, especially in upper part, the outer rim; epithecium colourless, inspersed with small crystals forming a sharply delimited layer; 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, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall K/I-, but the thin outer gel K/I+ blue, Bacidia-type. Ascospores (3-)5-15-septate, hyaline, acicular, curved or sigmoid, 65-100 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: thallus without 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)