96 THE ‘‘BLUING’’ AND THE ‘‘RED ROT” OF THE PINE. 
of examination, with high magnification, is a rather 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 fibers of the ‘‘ blue” wood show no indication 
whatever of any color element seen in the wood en masse. 
The hyphe constitute the only color element present in the ‘‘ blue” 
wood which could not be detected in the sound wood. These are 
present in the medullary rays and adjacent cells, as described above. 
These hyphx are pale reddish-brown, a color which may be obtained 
by taking a pale tinge of warm sepia. This color is very distinct and 
stands out in sharp contrast to the surrounding yellow wood fibers. 
(See Pl. VIII, showing the contrast.) How these brown hyphe 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 possibly 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 any 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 every 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 decay. It is true that 
the medullary 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. 
