English: Birch Polypore (Piptoporus betulinus). The British Mycological Society recommends both "Birch Polypore" and "Razorstrop Fungus" as colloquial names for this fairly common species, whose fruiting bodies are found from summer to autumn on the dead wood of birch trees.

For a view of the whole tree in context, see 1553991, where it is visible in front of the pine trees.

According to "Fungi of Switzerland - Volume 2: Non gilled fungi" (Breitenbach and Kränzlin), the undersurface of the fruiting body is cream-white when young, darkening with age, and the "old fruiting bodies are often attacked by the ascomycete Hypocrea pulvinata"; for a photograph of such an infection, see 1449039.

The same work notes that Birch Polypore "causes carbonizing rots"; these are also known as "brown rots".

[Two important kinds of fungal rot in wood are referred to as white rots and brown rots. Both attack certain constituents of the wood (cellulose and hemicellulose). White rots also attack lignin, making the wood pale, stringy, and fibrous. Brown rots leave lignin almost untouched, making the wood darker and more brittle, and often causing cubical patterns of cracks (see http://www.biology.ed.ac.uk/research/groups/jdeacon/FungalBiology/woodrots.htm ). Brown rots are of vital importance for forest ecosystems: they leave humus as their residue, and it is largely due to this residue that conifer seedlings often sprout along the line where a fallen conifer lay; see "Introductory Mycology" (Alexopoulos/Mims/Blackwell).]