Minnesota Plant Diseases. 



257 





celium of the fungus. These differ from the similar patches in 

 the Trametes root-rot in the usual absence of black centers. 



The fruiting body is brown and either forms a shelf or is 



diffused into a coating over 

 the bark. It is woody and 

 perennial, producing new 

 pore areas successively for 

 many years. The pore area 

 is on the lower surface of the 

 shelf forms and on the outer 

 surface of the prostrate 

 fruiting bodies. 



The oak Daedalea [Dcr- 

 dalca qnercina (L.) Pcrs.~\. 

 The cause of this disease is 

 a pore fungus and is not un- 

 common on the dead trunks 

 of oaks ; it is one of the most 

 common rots of oak railroad 

 ties. The fruiting body is a 

 thick shelf, woody in ap- 

 j>earance but in consistency 

 tough-corky. It is pale buff 

 in color and the upper sur- 

 face is smooth, though usu- 

 ally more or less zoned and 

 sometimes ridged. The 

 pore surface is often half- 

 cone-shaped and the p >res 

 are elongated from the cen- 

 ter toward the edge. The 

 |x>res are more or less sinu- 

 ous or wavy in outline and 

 are especially elongated to- 

 ward the point of attach- 

 ment. The jx>re surface is 

 of the same color as the top 

 of the shelf. 



