Volvariella bombycina

Scientific name:  Volvariella bombycina (Schaeffer:Fries)
Singer
Derivation of name:   Bombyc- means "silky" in reference
to the silky fibers of the cap.
Synonyms:  
Common name(s):  Tree Volvariella.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Pluteaceae
Occurrence on wood substrate: Saprobic; solitary or in
groups on deciduous standing trees or stumps or logs; July
through October.  
Dimensions:  Caps 5-20 cm wide; stipes 6-20 cm long
and 1-2 cm thick.  
Cap:  White to yellowish-white; dry, silky-fibered.
Gills: Free; white at first, becoming pinkish.
Spore print: Salmon to pink.
Stipe: White; smooth; dry; surrounded at base by a
membranous volva.
Veil: Absent.
Edibility: Edible.
Comments:  These mushrooms often grow out of wounds
in trees.
  
More information at MushroomExpert.com:   

Figure 1. Volvariella bombycina growing from the base of a
sugar maple tree (Acer saccharum) in a residential
landscape. Photo © John Dawson.

Figure 2. The whitish cap is covered with silky fibers. Photo
© John Dawson.

Figure 3. The stipe arises out of a volva, the remains of a
universal veil. Photo © John Dawson.

Figure 4. The pinkish gills are free from the stalk. Photo ©
William Roody.