20 THE "BLUING" AND THE "BED EOT" OF THE PINE. 



development is probably very similar, although it was not possible to 

 make an accurate determination of this fact because of the great 

 irregularity in the rate with which infection takes place after the 

 beetle attack. The rate of growth in the trunk varies considerably. 

 Some trunks are invaded on all sides with equal rapidity; some, on the 

 other hand, seem to be more resistant on one side or another. A good 

 idea as to the presence or absence of the fungus can usually be obtained 

 by observing the extent of the blue coloration, to which reference is 

 made below. 



EFFECT OF "BLUE" FUNGUS ON THE TOUGHNESS OF THE " BLUE " WOOD. 



On page 13 it was stated that the "blue" wood was considered 

 very much tougher than the healthy wood. The tie cutters in the 

 Black Hills find that it is very much harder work to cut cross-ties from 

 the "black-top" wood than from green trees so much so that they 

 demand additional pay for cutting these ties. 



When split with an ax, the two halves of a block seem to hang 

 together more firmly, and it requires more strength to wedge them 

 apart. Chips do not fly off as easily. The only explanation which 

 can be suggested for this peculiar behavior of the diseased wood is 

 that in the t; blue" wood we have an enormous number of filaments, all 

 extending radially through the wood. These filaments occur in 

 bunches, much interwoven, scattered at regular intervals through the 

 wood. It is estimated that at a point about 1 foot in from the bark 

 there are about 39,000,000 medullary rays per square meter of tangen- 

 tial surface, or about 3,700,000 per square foot. Even if the tensile 

 strength of one hypha is not very great, when it comes to 4,000,000 

 bundles these may have some effect in holding masses of wood fiber 

 together (see Plate VIII). This view is strengthened by the fact that 

 it seems easier to split the "blue" wood along radial lines than on 

 tangential lines. In making ties the tangential cut is used almost 

 entirely, and it is possible that these hyphal bundles are responsible 

 for the toughness. When split tangentially and viewed edgewise, one 

 can see some of these hyphal bundles projecting from the medullary 

 rays, as if they had been pulled out and stretched before being torn. 



RELATION OF THE "BLUE" FUNGUS INFECTION TO THE BEETLE HOLES. 



As has been previously stated, the first evidences of the presence 6f 

 the "blue" fungus are seen some weeks after the beetles have bored 

 into the cambium layer. The first signs of blue color in the wood 

 might be expected just under a hole in the bark or near such a hole, 

 or under the tube excavated in the bark extending from such a hole. 

 This, however, is not always the case; in fact, is rarely the case. The 

 small triangular patches of color may appear anywhere within the area 



