Agonimia octospora

About

Agonimia octospora is a species of corticolous, (bark-dwelling) squamulose (scaly) lichen in the family Verrucariaceae. This minute species has a thallus made of tiny pale grey-green squamules (scales) that are closely pressed to the bark of aged broadleaf trees, particularly oaks. It is distinguished from other members of the genus by features of its spores. The lichen occurs in ancient woodland habitats across parts of Europe and South America, showing a preference for minimally disturbed areas with abundant shrub coverage.

Summary from Wikipedia