12 THE "bluing" and THE "RED ROT " OF THE PINE. 



vicinity of the attack. Tlie first signs of the blue color are found in 

 the base of the trunk. On PI. VI, fig-. 1, three sections of a tree which 

 was attacked the latter part of Juh^, 1901, ai'e shown. The sections 

 were cut in November, 1901, at points 5 feet, 16 feet, and 36 feet from 

 the ground. The sapwood of the first section, 5 feet up, is entirely 

 blued; the second section, 16 feet up, is blue here and there; while the 

 section made in the top, 36 feet up, is without a particle of blue color. 

 Note in this connection that the sections with blue color show the cross 

 sections of the galleries of the bark beetles {Dendrocto7iu8 ponderosse) in 

 the laj^er formed by the cambium layer, the outer wood, and the inner 

 bark. The sections on PI. VI, fig. 1, show some of these galleries filled 

 with sawdust. A more advanced stage is shown on PI. VI, fig. 2. In 

 this tree the sapwood is blue from the ground up into the extreme top. 

 The smallest section, cut from the tree in the upper part of the crown, 

 is blue with the exception of the innermost rings, i. e., the beginning 

 of the heartwood. 



The blue color dev^elops ver}^ rapidl}" when once the tree is attacked. 

 Standing trees attacked by the beetles in Jul}', 1902, showed signs 

 of blue color in three weeks. T'hree months after the attack the 

 sapwood of the lower part of the trunk is usually entirely blue, as 

 shown on PI. I. The year following the attack, i. e., when the trees 

 have reached the "sorrel-top'' stage, the bluing has reached the top, 

 and late that 3'ear, when the "red-top" stage is reached, the entire 

 sapwood is blue (PI. VI, fig. 2). 



An experiment was made during the past sunmier to see whether 

 the blue color would appear in trees felled Ijefore being attacked by the 

 pine-bark beetle. It may be said at this point that they did "blue" 

 just as the standing ones did. 



naturp: of the "blue" wood. 



Some weeks after the attack by the liark beetles, changes take place 

 in the bark and the newer wood which ultimately result in the bark 

 becoming loose and separating from the tree. When the first flow of 

 resin into the galleries has stopped, the air enters into the galleries, and 

 channels of communication with the outside are established through 

 which the water in the cambium and newer wood can escape. The 

 result of this is that a moist atmosphere prevails in the air chambers, 

 very favorable to the growth of fungi. As the cambium and bark 

 cells lose water they shrivel and break from one another, so that after 

 a few months the bark breaks away from the wood proper. On the 

 south and southwest sides of the trees the bark dies most rapidly, and 

 here, contrary to the general occurrence, it frequently adheres firmly 

 to the tree. On the shaded sides of the trunk the bark becomes 

 loosened, as described, before six months have elapsed. The surface 

 of the wood is moist, very dark in color, and feels somewhat clamm\% 



