yo Journal of Agricultural Research voi. iii, no. i 



both upward and downward through the heart of the tree. When it 

 enters near the base of the tree, it sometimes spreads upward throughout 

 the heart of the entire trunk. This occasionally was noted in the white 

 oak in Arkansas, and such trees were worthless for lumber. 



In Oklahoma and to the west oaks frequently have large dead branches 

 at any point on the trunk of the tree. Through these the fungus may 

 enter. The rot therefore is not confined as closely to the upper half of 

 the trees as it is in the oaks of Arkansas and to the east. Probably 50 

 per cent of the western oaks attacked by this fungus have the rot through- 

 out the entire trunk. 



The sporophores of Polyporus dryophilus when growing on oak are 

 usually found only on living trees; however, specimens have been col- 

 lected growing on the boles and large branches of trees which had been 

 cut for at least three years, and in one instance a sporophore was found 

 growing directly on the top of an old oak stump. The fungus apparently 

 continues to grow slowly in the infected trees after they have been cut, 

 but rarely fruits under such conditions. There is no evidence at hand 

 concerning the possibility of infection by P. dryophilus after the death of 

 the tree. 



In no instance in Arkansas has the junior writer found this fungus 

 entering a tree through fire scars or other wounds on the butt of oaks, 

 even where fiire scars were common. The rot always originated at some 

 point above the base of the tree, and if a tree was found in which the rot 

 had reached the collar of the tree it came from above and not from below. 

 All of the sporophores of this fungus found on specimens of Populus were 

 growing on dead or dying trees. In this case the fungus is able to fruit 

 abundantly on both Hving and dead trees. 



This fungus on Populus seems to be truly parasitic, to some extent at 

 least. It attacks the trunks of the trees chiefly, entering the heartwood 

 through dead limbs after they are broken ofiF. The trees die by either 

 breaking off or in some cases apparently from the direct effect of the fun- 

 gus, which attacks the sapwood when the disease becomes far advanced. 



Several instances were found in oak where the fungus had apparently 

 penetrated and killed small areas of the sapwood and formed its sporo- 

 phores at these points. 



No positive evidence was found indicative of the age of the fungus in 

 either oaks or poplars or of its rate of growth in the infected tree. Appar- 

 ently trees of all ages are susceptible to this rot, provided the branches 

 are old enough to have formed heartwood. 



SPOROPHORE OF POLYPORUS DRYOPHILUS 



Polyporus dryophilus has a hard, granular, sandstone-like core, a 

 character that is unique and not possessed by any other polypore known 

 to the writers. The sporophore of this plant, represented by numerous 

 specimens collected by the writers in various portions of the United 



