Fomes fomentarius

About

Fomes fomentarius is a perennial wood-decay basidiomycete found in Europe, Asia, Africa and North America. The species produces large, hoof-shaped polypore fruit bodies which vary in colour from silvery grey to almost black, though they are normally brown. It develops on the trunks of various hardwood species and is associated with the development of white rot in the underlying wood. It has traditionally been described as a plant pathogen, but experimental studies have also reported its occurrence as a latent stem endophyte within apparently healthy trees.

Summary from Wikipedia