Order: Arthoniales       Family: Opegraphaceae Species: Opegrapha cesareensis Growth type crustose. Chemical reactions negative Photos: On coastal rocks. Allihies, Co. Cork, SW Ireland. The thallus is usually thin and smooth, whitish or pale grey and often tinged lilac with prominent scattered, simple lirellae (to 2mm long). A thin, dark prothallus is often present. Spores are 4-5(-6) septate, 13-24 x 4-5 µm. Microscope photograph below. Occurs on damp, shaded siliceous coastal rocks in gullies and crevices and below cliff overhangs Similar: Opegrapha calcarea. Spores 3-septate

Microscope photograph

Opegrapha cesareensis. March 2012