Heteroplacidium fusculum # Initially lichenicolous. Photographs on Aspicilia calcarea Initially parasitic on the thallus of Aspicilia calcarea before forming an independent thallus. Dark brown, deeply cracked thallus with flat or slightly convex areoles that become widely separated. The black perithecia are very small and hardly visible. Asci 8-spored, spores subglobose, 10-11 x 8-10 µm. Similar: Could be confused with Verrucaria nigrescens.

Heteroplacidium fusculum
On Aspicialia calcarea, Portland, Dorset. February 2016