This enormous wood-rotting (saprophytic) fungus, Meripilus giganteus, is a relatively soft bracket, and it grows very quickly. It is the fruiting body of the fungus; the rest of it consists of little feeding tubes (hyphae) in the dead wood of the treestump, which was a Hornbeam, a hardwood. The discs are attached to short stalks, and are concentrically patterned, with tiny scales over the top surface. The underside is a mass of holes or pores, hence the name; each one is the opening of a little tube where the spores grow. Millions of them fall out and blow away; presumably one or two will find a suitable treestump to grow on.
