Order: Lecanorales Family: Porpidiaceae
Species: Porpidia cinereoatra
Photos: On rocks. Gougane Barra, Cork, SW Ireland.
Identified by John Douglass
Thick, cracked to areolate, creamy-white or greyish thallus with a black prothallus +/- visible between areoles. Numerous large, +/- flat apothecia. Discs are black, initially grey or white pruinose with glossy or matt black margins. Epithecium brownish-green. Asci 8-spored. Spores colourless, simple, 13-18 x 6-9 Ám.
Widespread throughout Ireland. Locally common on exposed siliceous rocks in upland and coastal areas. Medulla K-, C-, P-
Similar: Porpidia macrocarpa, medulla K+/- yellow, P+/- orange, spores 16-20 x 6-11.5 Ám.
P.crustulata, K+/- yellow, P+/- orange, spores 10-17 x 5-9 Ám.
Porpidia cinereoatra. August 2009