DECAY OF THE " BLUE 7 WOOD. 27 



After the wood has been dead for some time certain changes begin, 

 which in the end result in the entire decay of the wood. The dead 

 wood may or may not be blue, for the processes by which the wood 

 changes to decayed wood are the same for wood which is entirely 

 healthy and for the "blue" wood. 



THE "RED ROT" OF THE WESTERN YELLOW PINE. 



The "red rot " of the western yellow pine usually starts in the tops of 

 the "black-top" trees, i. e. , trees which have been dead for two or more 

 years. At one or more points, usually on the north or east side of a tree, 

 one will find that the wood immediately under the bark starts to rot. 

 This rot starts at the bark and gradually extends inward (PI. X, fig. 1). 

 The wood when it shows the first signs of this decay is wet and soggy 

 and rapidly becomes brittle, so that it crumbles into small pieces when 

 rubbed. A plane will no longer make a smooth surface (PI. X, figs. 1 

 and 2), for the knife tears out small pieces of the wood fiber. The 

 color of the wood changes from blue to red yellow. When the decay 

 has gone on for some time, bands and sheets of a white felty substance 

 are found filling certain cracks which result because of shrinkage in 

 the wood mass (PI. X, fig. 2). These white sheets consist of masses of 

 fungus threads densely interwoven. The destruction of the wood con- 

 tinues until the heartwood is reached, and as this is exceedingly small 

 in the tops of these trees one will find that after some time almost 

 the entire wood mass has changed to a brown, brittle, resistless mass 

 (PL XI). The completely rotted wood crumbles into a fine powder 

 when crushed between the fingers. When wet it is of a cheesy con- 

 sistency. When the water has evaporated from such wood it is like 

 so much brown charcoal. 



The "red rot" of the dead timber is caused by one of the higher 

 fungi which grows in the wood, and by so doing brings about the decay 

 of the wood. The spores of this fungus fly about in the forest and 

 some of them lodge in bark crevices of the dying trees. The numerous 

 beetle holes afford every opportunity for entrance to the wood, and it 

 is therefore not surprising to find that the majority of the "black-top" 

 trees become infected sooner or later with the spores of this fungus. 

 The spores germinate and hyphie grow into the dead cambium and the 

 wood, where they attack such organic matter as has been left by the 

 "blue" fungus. They go farther, however, and attack the cell walls 

 of the wood fibers, from which they extract the cellulose. As a 

 result of this, the wood fibers shrink in volume and crack in regular 

 lines extending obliquely across the cell walls. As the solution of the 



