Arthonia graphidicola

Arthonia graphidicola is a species of lichen-dwelling fungus in the family Arthoniaceae. The fungus forms tiny reddish- to dark-brown flecks that initially develop beneath the bark surface before breaking through, typically measuring about 0.06–0.16 mm across or forming elongated structures up to about 0.4 mm long. It produces ascospores that are initially colourless and smooth but later become covered in dark brown granular warts, with the upper cell larger than the lower ones. The species is known from western Scotland, where it grows exclusively on the script lichen species Graphis scripta found on hazel bark in mild, oceanic districts....read more on Wikipedia.