Meripilus sumstinei

Scientific name:   Meripilus sumstinei (Murr.) Lars. et
Lomb
Derivation of name:   Meripilus means "part of a pileus."
Synonymy:  Meripilus giganteus (Fr.) Karst, Polyporus
giganteus Fr.
Common names:   Black-staining polypore.
Phylum:   Basidiomycota
Order:   Polyporales
Family:  Meripilaceae
Occurrence on wood substrate:  Parasitic and saprobic; on
ground (from roots) around stumps or living deciduous trees,
especially oak; July through November.  
Dimensions:  Individual caps 5-20 cm wide, forming large
dense clusters attached to a short, thick common stalk; stalks
(when present) 1-3 cm long and up to 11 cm thick.   
Upper surface: Grayish to yellowish-tan, becoming smoky
and dark with age; radially wrinkled; finely hairy; bruising
black along the margins where handled or in age. 
Pore surface: White; bruising black; pores 4-7 per mm.
Edibility: Edible.
Comments: Clusters of Meripilus sumstinei may attain
diameters of 40 cm or more.

More information at MushroomExpert.com:   
    

Figure 1. Terestrial rosette of Meripilus sumstinei at the
base of a tree trunk. Photo © Tom Schulein.

Figure 2. The rosettes in the foreground, parasitizing
the roots, are some distance from the trunk of the
host tree.

Figure 3. Note the blackish bruising on some of the fronds
(caps) of this specimen.

Figure 4. A specimen collected at a NEMF foray. Older
specimens become darker with age.

Figure 5. The cap surfaces turn black where touched.


Figure 6. The pores of Black-staining polypore are very
small, giving the pore surface a uniformly white, almost
"pore-less" appearance. Where touched, the pores stain
black.