Arthonia subfuscicola  

Thallus: absent (lichenicolous).
Anamorph: not known.
Teleomorph: ascomata arthonioid apothecia, 200-300 µm diam., sometimes coalescing to form compound structures to 600 µm diam., developing within the medulla of thallus areoles with the host cortex often persisting above the ascomata, or taking over the host hymenium; ± round to irregularly lirellate. Disc black, ± flat to slightly convex, not pruinose, true exciple not clearly differentiated.  Epithecium olivaceous brown, 10-12 µm thick, rather amorphous in structure. Interascal tissue composed of pseudparaphyses ca 2 µm diam., the uppermost cells usually inflated, covered with a granular pigment. Hymenium 40-50 µm thick, hyaline, I+ blue. Subhymenium 10-25 µm thick, hyaline to grey-brown. Asci clavate, 39-44 x 15-18 µm, clavate, thick-walled and fissitunicate, the tholus with a KI+ blue ring, 8-spored. Ascospores 15-17.5 x 5.5-7 µm, clavate, 3-septate, distinctly constricted at the septa, persistently hyaline or eventually becoming pale brown, fairly thick-walled, smooth, with a gelatinous sheath.
Chemistry: lichen products not known.