PINE DISEASES 295 



only to that caused by the pecky wood-rot. One or the other 

 of these wood-rots may predominate in a given region, and 

 combined they constitute a serious menace to young and old 

 trees. The two rots are also often found in the same tree, the 

 one in the roots and lower trunk and the other in the upper 

 trunk and branches. 



Symptoms. 



The decay is first evident in the heartwood of the roots. 

 The affected wood becomes yellowish and soon splits along 

 certain medullary-rays and annual rings into large cubical 

 masses. The wood in this stage of decay is soft and cheesy. 

 In the final stages, the wood is uniformly rotted, brittle, char- 

 coal-like and red-brown in color. From the heartwood of the 

 larger roots, the fungus may spread into the base of the trunk. 

 At times the rot may extend upward in the trunk for several 

 feet. The usual effect of this wood-rot is the uprooting of the 

 weakened tree by the wind. 



The sporophores of the causal fungus are soft, annual bodies 

 and grow from exposed or superficially buried roots. They 

 are red-brown, umbrella-shaped bodies with a central stalk 

 and circular, undulating top. They often grow to a large 

 size, being a foot or two across. The under surface of the cap 

 is covered with numerous large, shallow and irregular pores. 

 When old, a sugary solution is exuded from the under surface 

 of the sporophores and insects quickly destroy them. 



Caiise. 



The red-brown root- and butt-rot of conifers is caused by 

 Polyporus Schweinitzii. The roots are infected by the my- 

 celium growing in the soil from tree to tree. Also the spores 

 produced in the shallow tubes of the fruiting-body may infect 

 the wood which is exposed at fire wounds. For a general dis- 

 cussion of the life history of wood-rotting fungi, see page 64. 



