242 



Bulletin 193. 



toward the centre by a broad and irregular discolored area. The 

 discolored area is of a light brown color, cind tliis is farther sharply 

 defined from the pale yellowish white area outlined by a narrow 

 black line. The more advanced stages of decay in this maple tree 

 advanced toward the peripliery in separated columns, showing 

 on cross section a radiatino- or digitate fig-ure. The radiations or 

 '•fingers," alternate with dark areas which extend inward from the 

 periphery as shown in the photograph. Sometimes this figure is 

 quite regular around a portion of the margin, while other portions 

 are very irregular. The decay of the wood seems to proceed in 



76. — Toung trunk of maple nearly killed by Polyjwrus 



igniarius. 



waves from the centre towai'd the periphery, so that there appear 

 several different stages. The outer one is marked by the dark 

 discolored area, the next is pale yellowish white, the wood being 

 (juite soft, and an older and more advanced area at the centre 

 of the heart. These different stages in the process of decay 

 from the centre to the peripliery are usually limited by the black 

 line, which is bordered l)y a more or less well defined corona of 

 color darker than the area upon wdiicli it is advancing. In 



