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trees only, and most of the cases of which I have knowledge 
occurred in the southern portion of the state. 
The separation between wood and bark in those cases 
examined occured near the ground, and was not noticeably 
confined to any particular side. 
In most cases the bark appeared discolored over a por- 
tion of the separated area, and more or less ruptured as if 
from lateral tension in drying. Between the discolored 
portion and the limits of the affected areas the separated 
bark often appeared perfectly healthy, and in some cases 
new growth was protruding into the space between bark and 
wood. A few cases were found that gave no visible sign of 
injury beyond a slight change from the normal color of the 
bark, d'here was nothing to indicate the size of the affected 
areas; the bark was smooth and apparently healthy, but 
when struck emitted the hollow sound that proved a sure 
test of the extent of the injury. In cases of this kind it 
would seem that considerable time might elapse between 
the working of the cause and the discovery of its effect, and 
I apprehend that the first evidence of injury would be seen 
in a generally unhealthy appearance of the foliage of the 
tree. Of course, if the trunk was affected to the extent of 
girdling it, the tree would soon die. If the affected area 
was confined to one side the tree might endure for some 
years, but with vitality diminished in proportion to the 
extent of the injury. 
Where small areas only are affected the tree may by 
the intrusion of newly formed tissue, completely cover the de- 
nuded wood and thus effect a cure. From the location of this 
trouble beneath the bark, and from the tardy appearance 
of any evidence of injury, it is clear that a practical demon- 
stration of the cause would be difficult if not impossible. 
I am not aware that any actual demonstration of the work- 
ing of the cause has ever been made. Since the trouble 
became known its origin has been assigned to the action 
of frost, but there was no tangible basis for the assumption 
until the matter was taken up and critically studied by 
Professor Burrill of Illinois. The results of his observa- 
tions and the theoretical deductions from them were 
presented in a paper before the American Association for 
the Advancement of Science at the Ann Arbor meeting in 
1885. After explaining frost cracks, and the phenomena 
attending the crystalization of liquids by frost, he says — 
“The second form of injury — especially prevalent in apple 
trees — is believed to be due to the growth of ice crystals 
studding in a close or dense layer, the surface upon which 
