Species: Porpidia crustulata
Photos: Gougane Barra, Cork, SW Ireland.
Identified by John Douglass
Very thin cream or pale-grey thallus that is sometimes only visible as a dark stain and can be reddish near water. The abundant black, convex apothecia (approx 1mm diam) are usually in lines or groups. Asci 8-spored. Spores colourless, simple, 10-16 x 6-9 Ám.
Porpidia soredizodes is probably the sorediate counterpart.
Medulla usually K+ yellow, C-, P+ orange
Common on siliceous rocks, stones, pebbles and upland scree.
Similar: Porpidia cinereoatra
Immediately above: Porpidia crustulata, the Burren, April 2009