Chicken of the woods is a large, bright yellow-orange
fungus Laetiporus sulphureus that splays out from the side of trees, and is said to taste like
chicken. It is also known as sulphur
polypore, and
Polyporus sulphureus is one of the more common of its taxonomic synonyms.
It lives on dead and dying wood, principally oak and yew, and while the spectacular stacked wings of the fruiting body appear on the outside, in spring and summer, it is all the time feeding on the heartwood of the tree, turning it into a brick-red mass that breaks up into cuboidal chunks. This is the remains of the lignin, as chicken of the woods digests only the cellulose. It is one of the processes that makes a tree hollow, disposing of the inner rings of the xylem that it is no longer actively using.
The younger, outer edge of the fungus is the tender part that is worth eating, and needs to be cooked, as upsets have been reported from the raw fungus. I haven't recently (since learning they were edible) seen any close enough to the ground to get to and try.
Kingdom: Fungi
Phylum: Basidiomycota
Class: Basidiomycetes
Order: Polyporales
Family: Polyporaceae
pictures:
http://www.wimpole.org/fungi01.html
http://www.bioimages.org.uk/HTML/P4/P49397.HTM
http://www.first-nature.com/fungi/id_guide/poriales/laetiporus_sulphureus.htm
Of cellulose and lignin:
http://www.woodland-trust.org.uk/ancient-tree-forum/information/ecology/natural_info.htm
Full list of synonyms:
http://indexfungorum.org/Names/SynSpecies.asp?RecordID=299348