Order: Lecanorales       Family: Lecideaceae Species: Lecidea lithophila Growth type crustose. Photos: On upland rock. Gougane Barra, Cork, SW Ireland. Left identified by John Douglass The cracked-areolate thallus is greyish, usually with patches that are stained rusty-red. Large, +/- flat apothecia are dark-brown to black, becoming browner when wet. Asci 8-spored. Spores simple, colourless, 11-15 x 5-6 µm. Microscope photograph below. Common in upland areas, often near streams on iron-rich siliceous rocks. Chemical reactions negative. Similar: Tremolechia atrata and Rhizocarpon oederi

Microscope photograph

Lecidea lithophila. August 2009 and January 2012