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10 THE "BLUIKG and THE "RED ROT OF THE PINE. 



and there one will find the needles of affected trees turning j-ellowish. 

 The bright green fades almost imperceptibly, starting near the tip of 

 the needle. The needles first affected are those on the lowest branches 

 (PI, II), and on these branches the discolored leaves will be more or 

 less scattered. B}^ the end of Ma}' most of the leaves on an affected 

 tree will be pale green or yellowish. (PL II; PI. Ill, 2.) This yellow 

 color increases in intensity during the summer and makes the affected 

 trees a conspicuous mark among the healthy green trees. Trees in this 

 stage are locally known as ''sorrel tops" or 'S'ellow tops." When 

 standing on a hillside, groups of "sorrel tops" can be easily detected at 

 a distance of several miles. It is rather a difficult matter to show the 

 contrast in a photograph. The middle tree on PI. II, fig. 1, shows the 

 contrast with the green trees on the left to some extent. 



The yellow needles are drier than the green ones and show a marked 

 disintegration of the chlorophyll. As the}- continue to dry the color 

 changes gradually through various intermediate stages (PI. Ill, 3) to 

 a reddish brown. This color (PL III, 4) becomes very marked after 

 the trees have passed through the second winter. The needles are 

 then dry and thev begin to fall off'. Such trees are known as "red 

 tops." \See PL 11, fig. 1; PL IV, fig, 1.) The leaves finally fall off 

 completely, leaving the branches bare. Such trees without any leaves 

 are known as '"black tops." (PL IV, fig. 2.) The group of trees on 

 PL II, fig. 1, shows the green trees and the "sorrel tops" and "red 

 tops" (rapidly becoming •'black") side by side. 



To summarize the foregoing: One finds the living trees attacked in 

 July and August; the following spring the leaves turn yellow ("sorrel 

 tops") and gradually red ("red tops"), and the third year they drop 

 off' altogether ("• black tops"). It is a difficult matter to say at what 

 point the trees are dead. Girdled trees die with different degrees of 

 rapidity, depending upon the species. The black gum {M/ssa sylvatica) 

 will live — i. e., will have green leaves — for two years after being gir- 

 dled; so also several species of oak. Pines and spruces rareh' live 

 more than a year, and generall}- not so long. 



The reason for the different behavior of these trees is probably to 

 be found in the different power to conduct Avater through the inner 

 sapwood. The subject is one about which little is known as yet. In 

 the case of the bull pine, after the girdling by the beetles certain 

 changes take place in the cambium and the newer sapwood which 

 leave no doubt as to the death of those parts. By September, as 

 described below, the cambium and bark are actualh' dead and par- 

 tially decayed for 30 feet or more from the ground. The leaves are 

 still green and full of water the following spring. The only way in 

 which this can be accounted for is by assuming that sufficient water 

 passes through the inner sapwood to keep the crown of the tree 

 supplied 



