20 The Colorado Expp:riment Station. 
and blackened. The other two sections of the root were still of a 
natural color. The roots, two in number which were thrown off 
to the left of the main root presented a condition contrasting very 
sharply with the five rootlets and the two sections of the main root 
for they were apparently entirely normal while the others were black 
and dead. The condition of this root is shown in Plate VIL, Fig. 
I, which represents a section of the root taken close to the trunk 
'of the tree—again in Plate VIL, Fig. 4, which represents a view of 
the under side of a piece of this root. The side root was ap¬ 
parently healthy (Plate VIL, Fig. 3). The killing of the bark and 
woody tissue was in this way traced from the point at which the 
sodic arsenite was introduced into the ditch through the small 
roots into the large one, thence into the trunk, the limb, and even 
into the branches. The course was direct and the flow of the poi¬ 
sonous solution was confined to a comparatively narrow channel. 
The darkened area, “black heart,” in the case of these branches is 
shown in Plate VIL, Fig. i-a and upper Fig. 2, which shows tiie 
central discolored area, which is not symmetrical with the annual 
rings or contour of the limb, and also the border of deeper stained 
tissue. I am not concerned about any theory of sap circulation, but 
am simply tracing the discoloring effect of the arsenic through the 
root into this portion of the branches. We see that the discoloration 
extends through the root, trunk and central portion of the branch. 
In this instance, death may be said to have been sudden and it may 
be assumed that a portion of this effect may be a post mortem one. 
We have not simply assumed that the placing of sodic arsenite 
in the ditch and the dying of this branch of the tree two days 
later are wholly conclusive as to the cause of death. I have ex¬ 
amined the wood of the branches and the root and find an abund¬ 
ance of arsenic in both. In this case, I recovered the largest amount 
or arsenic found in any sample, namely from the discolored portion 
of the root, in which I found arsenic corresponding to 34.5 parts 
of arsenic acid in one million parts of the tissue. 
The other portions of this tree were apparently in good condi¬ 
tion when I last saw it. An examination of the branches from the 
unaffected portion failed to show any such case of “black heart” 
as the affected limb (Plate VIL, Fig. i-b). In fact, they showed 
nothing which could be classed as a darkened center, though I recall 
one branch which was clouded more or less. 
I have given this case in some detail because I believe it to be 
as conclusive proof as can possibly be'adduced that soluble arsenic 
compounds not only produce death when introduced into the circula¬ 
tion of the apple tree, but will produce the effects which we find pre¬ 
ceding the death of our apple and pear trees. In both cases, we 
have the killing of the bark, the staining and destruction of the tis¬ 
sue, and the killing of the trees. The “black hearted” condition is 
