[Microthelia subfuscicola Linds.]
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Life habit: lichenicolous Thallus: inapparent Ascomata: ±round to irregularly lirellate (especially when on thallus), sometimes exceeding 0.2 mm in width disc: black, ±plane to becoming more slightly convex, epruinose epihymenium: olivaceous brown, 10-15 µm thick, uppermost cells usually inflated, otherwise cells c. 2 µm wide, with a granular pigment hymenium: hyaline, 40-50 µm tall; sub-hymenium: hyaline, 10-25 µm thick asci: clavate, 40-45 x 15-20 µm, 8-spored ascospores: persistently hyaline, 3-septate (not incised), narrowly ovoid, 15-17.5 x 5.5-7 µm, with a slim gelatinous epispore Pycnidia: not seen Chemical reactions: ascomatal gels I+ (blue turning) red; ascus tholi with KI+ blue ring-structure; epispore I+ red, KI+ blue. Substrate and ecology: on thallus and ascomata of Lecanora albella, L. carpinea, and L. chlarotera World distribution: Europe and North America Sonoran distribution: southern Arizona (Pima Co.). Notes: Arthonia subfuscicola is rather similar to Arthonia varians, but differs by its occurrence on both ascomata and thalli of bark inhabiting Lecanora species. Ascomata found on the thalli can become large and cracked in their centers.