Bracket Fungus

A bracket fungus, probably Heterobasidion annosum, growing on the stump of what I think was a birch tree (Betula sp). 

I took a small sample from the edge to examine with a magnifier at home.  It showed 2 to 3 pores per mm on the underside.  The pore tubes were about 5mm long.  Under x600 on the microscope I was unable to find any clamp connections. These details are consistent with the fungus being H. annosum.

[Note added 2012-12-24: I managed to get some spores from a small sample of this fungus.  These spores were about 10 x 8um.  This is too large for H. annosum.  It is more likely a Ganoderma sp, maybe Ganoderma resinaceum.]

Photos taken in the Wilderness, Whiteknights Park, Reading, UK, on 2012-11-22.