46 
CAROLINE RUM BOLD 
chestnut blight fungus; one had just been girdled at the base of the tree. 
The stain extended into the branches and roots, sometimes but part way, 
sometimes to the beginning of the year's growth. In no case did it extend 
beyond the beginning of the new year's growth of twigs and roots. At the 
point of injection it had penetrated three annual rings of wood and was 
found in the bark. However it was soon confined to the last annual ring 
in the neighborhood of the vessels. The girdled tree showed the stain 
passing through the diseased area by way of the vessels and tracheids; 
traces of it were found in the bark where disintegration had just begun. 
It will be noticed that the results of injection in 1912 and 1913 differed. 
No experiments were undertaken to discover the cause of this difference. 
As stated before, most of the dye passed through the xylem elements 
of the last formed annual ring. At first it entered the large spring vessels, 
which appeared, however, not always to be the carriers. The summer 
tracheae or vessels, which in cross sections of Paragon chestnut form char- 
acteristic flame-like lines of pores diverging from the spring vessels, were 
deeply stained, and so were the tracheids. The trees injected with methy- 
lene blue showed ragged tissues and holes in the neighborhood of the spring 
vessels. There were traces of dye found in some of the vessels of the new 
growth of wood near the point of injection, but generally this new growth 
was unstained. 
A microscopic examination of the xylem cells showed that the dye 
was retained by the walls of the vessels and tracheids through which it 
passed. 
These phenomena (the decreasing size of the injected area and the 
gradual dilution of the solution as the distance from the point of injection 
increased) were observed when solutions of salts were injected into growing 
trees. Though the paths could not be followed as easily as when dyes were 
used, they could be traced, often, by a formation of abnormal bark tissue 
which disappeared as the distance from the point of injection increased. 
When a "killing" solution was injected the path was marked on the trunk 
by vertical strips of dead tissues. Those twigs and branches whose vascular 
system entered this path were killed; often but one side of a branch was 
affected. All stages of reaction to an injection could be seen in a tree: 
dead tissue at the point of injection in the trunk, dead or falling leaves on 
the branches nearest the injection hole, spotted leaves on branches higher up 
the tree, and no signs of injection visible in the top of the tree. 
Time of Injection and Dilution of Solution 
The way in which a tree was affected depended both on the time of the 
injection and on the dilution of the chemical solution. Concentrated solu- 
tions acted more quickly than dilute ones and generally were injurious.^ 
3 "Experiments on the Ph or true acidity values of normal and cankered chestnut bark 
adjacent to the cambiam layer show that healthy chestnut bark has a Ph of about 4.8, 
