Fungus on oak

[Electrictree]

Several fruiting bodies between the buttresses of a veteran oak (Q. robur) The old ones are concrete-hard; the small young growth is hard but can be cut with a sharp knife and some difficulty to reveal a mahogany-brown iterior with no discernable tube layer.

Any ideas??

[David Humphries]

I suspect this is Ganoderma adspersum.

 

The dark brown flesh in the 3rd image rules out Phellinus or Fomes.

 

The white surface in your 3rd inage  is a feature of Ganoderma, whereas the under surface of Phellinus is a tan brown colour.

 

I also think I can see cocoa coloured spore on the edge of the cobweb in the 3rd image. 

 

Do you have a copy of the AA Fungi on Trees photographic reference book?

 

On page 77 in the section on perennial fruit bodies, image 4 (going clockwise) shows a tired bracket of G. adspersum that has a surface like your old fruit bodies which also shows a wedge of the flesh on top which is a close match to your 3rd image. 

 

Hope you find this helpful.