Species: Porpidia tuberculosa
Photos: On acid rock. Ballingeary and Gougane Barra, Cork, Ireland
Very variable. Whitish to blue-grey or greenish-blue, irregularly cracked, +/- smooth thallus, sometimes tinged orange-red. When present narrow prothallus is black or brown. Scattered or crowded pale grey or greyish-blue soralia, occasional black apothecia.
Chemical reactions negative.
Common on hard siliceous rocks, pebbles, walls and memorials, rare on worked timber.
Similar: Porpidia soredizodes . Soredia K+ yellow, C-, P+ orange
Porpidia tuberculosa. March and August 2009