Order: Arthoniales Family: Roccellaceae
Species: Opegrapha vulgata
Photos: Co. Cork and Co. Waterford, Ireland.
Identification of specimen in lower photo confirmed by J Douglass
Very variable. Thallus thin, smooth or +/- cracked, white, grey or brownish, often olive-tinged. Slender lirellae to 2.5 mm long, curved, straight, stellate or forming interlocking networks. Disc usually remains slit-like. Small black pycnidia are often present. Microscope photograph below.
Common, widespread throughout Ireland on shaded, smooth-barked trees. Also found on smooth areas of rough-barked trees.
Chemical reactions negative.
Similar: O. niveotra. Shorter discs to 1mm. Basic-barked trees.