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 

 73 is on the lower surface of the 

 | shelf forms and on the outer 

 surface of the prostrate 

 fruiting bodies. 



The oak Daedalea \D<z- 

 dalea quercina (L.) Pers."].. 

 A The cause of this disease is 

 a pore fungus and is not un- 

 I common on the dead trunks 



g 



5 of oaks ; it is one of the most 



common rots of oak railroad 



ex 



g ties. The fruiting body is a 

 thick shelf, woody in ap- 

 | pearance but in consistency 

 * tough-corky. It is pale buff 

 in color and the upper sur- 

 face is smooth, though usu- 



8 



ally more or less zoned and 

 M sometimes ridged. The 



1 pore surface is often half- 

 ^ cone-shaped and the pores 

 are elongated from the cen- 



2 ter toward the edge. The 

 pores are more or less sinu- 

 ous or wavy in outline and 

 are especially elongated to- 

 ward the point of attach- 

 ment. The pore surface is 

 of the same color as the top 

 of the shelf. 



