338 ECOLOGY. 



eventually makes its way to the outside of the tree trunk in 

 places, where large fruit bodies characteristic of the species are 

 found. Figure 443 represents a large sugar-maple tree which is 

 attacked by one of the wood-destroying fungi. The fruit bodies 

 here are of the shelving form and overlap. The fruiting surface 

 of this plant on the sugar maple is in the form of spines, instead 

 of gills, and belongs to the genus hydnum. A number of large 

 maple trees in the grove where this one stood were injured by 

 wood-destroying fungi, and many of them were so weakened 

 thereby that they were blown over during a southeast gale. 

 Some shelving fungi possess gills like agaricus. Others have 

 the under surface honeycombed as in polyporus. 



622. The roots of trees are often attacked by a mushroom, the 

 honey agaric (Agaricus melleus). The mycelium here forms 

 long black strands underneath the bark of the root. These often 

 extend from the roots up into the interior of the trunk of the 

 tree, causing decay. The roots are sometimes so weakened by 

 the fungus that they die and easily break when heavy winds arise. 

 Figure 444 shows such a tree uprooted. Further, it is broken 

 about midway of the trunk, because the trunk was weakened 

 by the mycelium inside. Other trees weakened by fungi, and 

 broken over during the same gale, are shown in the same figure. 



