458 



1 IXGOUS DISEASES OF PLANTS 



the variety of host plants upon which it is reported. This fungus 

 has been found practically throughout the world where trees grow. 

 It is unquestionably more abundant in humid climates, yet minor 

 or nonpersistent, unfavorable conditions do not readily affect it. 



This Polyporus is of special interest because of its occurrence 

 upon a large variety of trees. Deciduous trees are more commonly 

 attacked, yet both in Europe and America it is not infrequently 

 found upon conifers. It is perhaps oftener noticed upon such 



FIG. 226. POLYPORUS SULPHUROUS ON EXPOSED ROOTS OF A LIVING TREE 

 (Photograph by L. H. Childers) 



forest and shade trees as oak, walnut, butternut, ash, black locust, 

 poplar, and willow. Among orchard trees the cherry in old orchards 

 is a common host, but pear and apple trees are also susceptible. 

 Moreover, the sporophores of this fungus may appear upon fallen 

 trunks and stumps, and it appears to be true that the mycelium of 

 the fungus may develop extensively in fallen trunks. 



The coniferous trees upon which it has been more frequently 

 observed are the larch in Europe and the hemlock and spruce in 

 America. 



