262 Minnesota Plant Diseases. 



comes into contact with the living root of a tree it bores its way 

 through the outer bark into the soft bark and the growing re- 

 gion ; here it frays out into a fine felt-like expansion and attacks 

 the living cells. The latter are killed and the fungus proceeds 

 between bark and wood up to the stem and often for some dis- 

 tance up the latter. From the stem the mycelium may make 

 its way down into healthy roots. The attack on the root sys- 

 tem results in the death of the tree by cutting off the supply of 

 crude materials. At the base of such a trunk one may later in 

 the autumn find the fruiting bodies. The mycelium in the 

 trunk and roots assumes the form of shoe-string strands and 

 these may grow into a very well developed net-work just under 

 the bark. The mycelium may continue to live on the timber 

 saprophytically after the death of the tree. This fungus has 

 often been reported as a timber-destroying fungus in mines. The 

 honey-colored mushroom attacks the oaks and probably other 

 broad-leaved trees in our state. In Europe it has been reported 

 as particularly destructive to coniferous woods, as well as to 

 broad-leaved trees. 



When the disease becomes epidemic, no successful combat- 

 ive measures are known. All diseased trees and fruiting bodies 

 should be burned and young trees should not be planted on in- 

 fected areas. (See also Figs. 6, 7.) 



The fatty Pholiota rot (Pholiota adiposa Fr.). On standing 

 trees and particularly on felled timber of oaks and other broad- 

 leaved trees, one often finds in fall clusters of a conspicuous, 

 bright-yellow mushroom, which is responsible for a white rot 

 of timbers. The fruiting bodies may be six inches or more in 

 length ; the cap is bright yellow with concentric, blackish spots. 

 The latter are also found on the stem, which is about of equal 

 diameter throughout its length and is tough-fleshy. The cap 

 in moist weather is covered with a slimy gelatinous coat. On 

 the under surface of the fruiting body are gills radiating from the 

 stem as in the honey-colored mushroom. These gills are in this 

 case, however, yellowish to grey in color and throw off ochre- 

 brown spores, which often discolor the stem or other objects 

 upon which they fall. The mycelium attacks the wood and 

 forms bands of white felt which separate the wood up along 

 the lines of the annual rings. Although not infrequently met 



