Light grey lichen with dark soredia

Light grey lichen with dark soredia

Observation - Light grey lichen with dark soredia. Description: Light grey, crustose thallus with lots of cracks growing on angled ledge of siliceous sandstone church wall. Dark prothallus visible around some of the perimeter. Small spots and larger patches of dark soredia on surface of thallus. Possibly Porpidia tub

Light grey, crustose thallus with lots of cracks growing on angled ledge of siliceous sandstone church wall. Dark prothallus visible around some of the perimeter. Small spots and larger patches of dark soredia on surface of thallus. Possibly Porpidia tuberculosa.