26 THE "bluing'' and the "red rot" of the t^ine. 



of examination, with hi^h mag'nitication, is a ratiier uncertain one, 

 however, for the refraction caused by the containing liquids, which 

 are purplish, and of light falling- from a blue sky, is apt to show very 

 faint traces of color which do not belong to the wood. It may be 

 stated definitely that the libers of the " blue" wood show no indication 

 whatever of any color element seen in the wood en masse. 



The hyphffi constitute the onlj^ color element present in the "blue" 

 wood which could not be detected in the sound wood. These are 

 present in the medullary ra3\s and adjacent cells, as described above. 

 These hypha? are pale reddish-brown, a color which may be obtained 

 by taking a pale tinge of warm sepia. This color is ver}" distinct and 

 stands out in sharp contrast to the surrounding yellow wood libers. 

 (See PL VIII, showing the contrast.) How these brown hyphfe could 

 make a blue gray or mouse gray it is difficult to understand, for no 

 density of such a brown, even in combination with straw yellow (of 

 the wood fiber), could possibh" produce blue gray. It would there- 

 fore seem probable, or at least possible, that there is some pigment 

 with a blue element in the "blue" wood which is so faint that its 

 detection in thin microscopic sections becomes almost impossible. 



All efforts to extract an}- color of a blue nature from the wood have 

 so far failed. Extracts of blued wood with ether, alcohol, benzol, 

 chloroform, alkalis, and acids gave evidence that changes of some 

 sort had taken place in the wood fiber, for the extracts of sound and 

 " blue" wood differed materially in nearly ever}' instance. No signs 

 of any blue or blue-gray color were obtained. 



It seems necessary, therefore, to leave this matter for further inves- 

 tigations, which are now in progress. 



SUMMARY. 



In the foregoing chapters a peculiar disease of the dying wood of 

 the bull pine has been described. The wood turns blue in August and 

 September, after the trees are attacked by the beetles. The blue color 

 starts near the base of the tree and gradually spreads upward until 

 the entire sapwood is blue. The ' ' blue " wood is somewhat tougher 

 than the healthy wood and has been shown to be practically as strong 

 as the healthy wood. 



DECAY OF THE "BLUE" WOOD. 



The changes which the "blue" fungus brings about in the wood of 

 the western yellow pine can hardly be called deca\'. It is true that 

 the medullar}' rays are destroyed in part and that the walls of many 

 wood fibers are punctured, but as a whole the wood is sound in the 

 ordinary acceptance of that term. It is not rotten, or doty, or decayed. 

 The "blue" fungus attacks cell contents and not the cell walls. 



