Description: Thallus crustose, episubstratic, continuous to usually rimose-areolate, grey-green. Apothecia lecideine, 0.6-1.5 mm across, pinkish orange to orange-brown, rarely dark brown when old, epruinose or rarely white-pruinose, with an initially flat, later convex disc, and a smooth proper margin. Proper exciple straw-coloured to pale orange, or brownish orange in outer part, of radiating hyphae with gelatinized walls and 0.5-2 µm wide lumina, sometimes with radiating clusters of minute crystals soluble in N but not in K; epithecium more or less colourless, poorly evident; hymenium colourless to straw-coloured, 75-100 µm high; paraphyses mostly simple, 1-1.5 µm thick at mid-level, the apical cells slightly swollen; hypothecium straw-coloured, always somewhat darker than hymenium. Asci 8-spored, clavate, surrounded by a gelatinous I+ blue coat, with a well-developed I+ blue tholus, a I+ darker blue tube and a well-developed ocular chamber, Bacidia-type. Ascospores 7-15-septate, hyaline, needle-like, straight to sigmoid, (45-)50-85(-110) x (2.5-)2.6-3.5(-4.3) µm. Pycnidia immersed, pale orange-brown in upper part. Conidia simple, curved, 10-21 x 0.6-0.8 µm. Photobiont chlorococcoid. Spot tests: thallus K+ or K+ yellowish brown, C-, KC-, P-. Chemistry: thallus without lichen substances or with traces of atranorin.
Note: a mild-temperate, probably Mediterranean-Atlantic lichen found on deciduous trees, especially Acer, in open, humid deciduous woodlands; mainly Tyrrhenian in Italy. Some earlier records from Lazio (Castelporziano, see Nimis 1993: 110) and the Island of Marettimo in Sicily (Nimis & al. 1994) refer to B. tyrrhenica.
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)