Synonyms: Bacidia tuberculosa auct. non (Fée) Trevis.; Bombyliospora incana A.L. Sm.; Bombyliospora pachycarpa (Delise ex Duby) A. Massal.; Bombyliospora tuberculosa auct. non (Fée) A. Massal.; Megalospora tuberculosa auct. non (Fée) Sipman
Distribution: N - Frl. C - Tosc.
Description: Thallus crustose to subleprose, episubstratic, up to 0.2 mm thick, dull, yellowish white, pale grey-greenish or grey-white, not tuberculate, sorediate, forming large patches, without a distinct prothallus. Soralia at first more or less discrete, but soon becoming confluent, forming a more or less continuous sorediate crust; soredia fine to coarse, usually aggregated into up to 80 µm wide consoredia, often with needle-like projecting crystals. Apothecia very rare, rounded, (0.5-)1-2 mm across, with a concave to flat, dark brown disc and a paler or concolorous, raised, persistent proper margin. Proper exciple of radiating hyphae, compact in outer part, loose-arachnoid within; epithecium orange-brown, densely inspersed with granules not dissolving in K; hymenium colourless, 130-180 μm high, inspersed with oil droplets; paraphyses sparingly branched and anastomosing, slightly swollen at tips; hypothecium colourless. Asci 1-spored, clavate-subcylindrical, with a thick amyloid tholus and a I+ blue gelatinous outer layer. Ascospores 5-11-septate, hyaline, 70-160 x 25-35 µm, the wall c. 2 μm thick. Conidia short-bacilliform. Photobiont chlorococcoid (Dictyochloropsis), the cells 5-14 μm wide. Spot tests: thallus: K+ pale yellow, C-, KC+ yellow, P-, UV-. Chemistry: usnic acid, zeorin, unknown terpenoids.
Note: a mainly pantropical species found on old deciduous (mainly Fagus) and coniferous (mainly Abies) trees in humid montane forests, sometimes overgrowing epiphytic bryophytes. It is included in the Italian red list of epiphytic lichens as “Critically Endangered” (Nascimbene & al. 2013c).