Grifola frondosa
This late summer and fall mushroom is most often found
growing from base of oak trees. Also found beside other
hardwoods and conifers. Common names include Hen of the
Woods and Sheep's Head.  The Japanese common name is
maitake, which translates to "dancing mushroom".  

An edible mushroom sought out by many,
Grifola frondosa has
brown to grayish "fronds" that form from a branching structure.
Pore surface is white and does not bruise black.

Compare to
Merripilus sumstinei.
Ron Kerner
Cross section                 Pore surface                 Mushroom geek
Spore size 5-7 x 3.5-5 µ;
smooth, elliptical.
A fifteen pound specimen in pristine condition.
Described at
Fungi Growing on Wood