oom ed 
Fungus Diseases fet 
most common and the most insidious, since their mycelium 
penetrates deeply into the body of the tree out of reach. 
Since the trunk of the tree, the wood, is mostly dead tissue, 
Fic. 11. — Three species of rot fungi. When these fruit-bodies appear at 
the base or on the wounds of a tree, the interior is usually all decayed, and 
help comies too late. (After Murrill, from Cornell University Bulletin, No. 
205.) 
they do not impair to any great extent the living portion. 
Yet they are not mere saprophytes, for they really feed on 
the wood, absorbing cell-walls and cell contents, and to 
some extent impair its functions in the conduction of water. 
But their main damage lies in destroying the firmness of 
