10 THE ‘‘BLUING’’ AND THE ‘‘RED ROT” OF THE PINE. 
and there one will find the needles of affected trees turning yellowish. 
The bright green fades almost imperceptibly, starting near the tip of 
the needle. The needles first affected are those on the lowest branches 
(Pl. II), and on these branches the discolored leaves will be more or 
less scattered. By the end of May most of the leaves on an affected 
tree will be pale green or yellowish. (PI. II; Pl. III, 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 ‘‘ yellow 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 they continue to dry the color 
changes gradually through various intermediate stages (PI. III, 3) to 
a reddish brown. This color (PI. III, 4) becomes very marked after 
the trees have passed through the second winter. The needles are 
then dry and they begin to fall off. Such trees are known as ‘‘red 
tops.” (See Pl. I, 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.” (PI. LV, fig. 2.) The group of trees on 
Pl. Il, 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. Giurdled trees die with different degrees of 
rapidity, depending upon the species. The black gum (Wyssa sylvatica) 
will live—i. e., will have green leavyes—for two years after being gir- 
dled; so also several species of oak. Pines and spruces rarely live 
more than a year, and generally not so long. 
The reason for the different behavior of these trees is probably to 
be found in the different power to conduct water 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 actually 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 3 
