Order: Arthoniales Family: Roccellaceae
Species: Opegrapha herbarum
Photos: Ardnagashel and Macroom, Co.Cork, Ireland. Identified by Andy Acton and John Douglass
Thin or inconspicuous pale grey, brownish or olive-green thallus.The small, scattered lirellae are usually simple, less frequently branched. Slit-like discs becoming fully open, occasionally +/- green-pruinose. Pycnidia are very rare. Asci are 8-spored, spores 3-septate, 18-25 x 5-8 Ám with thin perispore. Microscope photographs below.
Occurs on acid to basic, smooth, often shady bark. Also found on plant stems (especially brambles) and sandstone.
Chemical reactions negative.