Arthoniaceae Arthonia graphidicola # Chemical results: Epithecium K+ dull olive Lichenicolous on thallus of Graphis scripta. Frequent in W Scotland, scattered records from elsewhere in Britain and Ireland. BLS conservation evaluation: LC NS Sc IR Thallus absent, scattered red to dark brown, rounded, elongate or fleck-like apothecia developing below the bark and then erupting through host thallus. Spores 2-3 septate, upper cells enlarged, (13-)14-17 × 4.5-5.5 µm. Initially smooth and colourless, becoming brown warted. Micro photo below. Similar: Stigmidium microspilum (black perithecia) also found on G. scripta. Arthonia thelotrematis occurs on Thelotrema lepadinum

Microscope photograph

Arthonia graphidicola
On Graphis scripta. Studland Heath and Chettle woods, Dorset. May 2015, December 2018