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 



■i is on the lower surface of the 



3 shelf forms and on the outer 



° surface of the prostrate 



° fruiting bodies. 



I The oak Daedalea [Dcb- 



» dalea quercina (L.) Pers.]. 



a The cause of this disease is 



° a pore fungus and is not un- 



I common on the dead trunks 



>2 of oaks ; it is one of the most 



common rots of oak railroad 



D. 



■S ties. The fruiting body is a 



1 thick shelf, woody in ap- 

 I pearance but in consistency 

 ° tough-corky. It is pale buff 

 j^ in color and the upper sur- 

 ° face is smooth, though usu- 

 ^ ally more or less zoned and 

 » sometimes ridged. The 

 •g pore surface is often half- 

 ^ cone-shaped and the pores 

 S are elongated from 'the cen- 

 ^ 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. 



