48 
CAROLINE RUMBOLD 
Ten days after being treated with potassium bichromate i/iooo G.M., the 
back of the tree cracked along the edges of the path of the solution. In 
July and August, Penicillium sp. grew luxuriantly in these cracks and in the 
points of injection. The following year all the trees injected with the 
chromate solutions were dead. 
The day after an injection of copper sulphate 1/20 G.M. was started, 
the leaves began to turn brown, those nearest the point of injection first. 
Copper chloride 1/20 G.M., zinc chloride 1/20 G.M., and barium chloride 
1/20 G.M. acted almost as quickly. All of these were "killing" solutions. 
As previously stated, the paths these solutions took up and down the tree 
could be followed by the visible killing of the tissues. The region they 
passed through was a narrow one, but little wider than the hole made for 
the injection. Those twigs and branches whose fibers entered this path 
showed dead leaves. The leaves were the first to show the effects those 
nearest the point of injection browning first. A smell of decaying plant 
tissue became noticeable (in the case of CU2SO4 1/20 G.M. in 10 hours, 
during which time i liter had been injected), which sometimes continued 
for one and two days. The dying leaves did not become crisp until some 
time after they had browned, in one case not until four days after browning. 
Environmental conditions probably influenced this phenomenon. Even- 
tually all the leaves on the trees died, and soon those on the parts of the 
trees not included in the paths of the solutions fell off. The leaves dropped 
as they would in the autumn. The denuded branches quickly produced 
new leaves, so that trees injected in August had full-sized green leaves in 
December. The dead leaves still hung on the injected branches, rendering 
them conspicuous. The following spring these trees leafed, and produced 
fruit like the surrounding trees. The branches which had been injected 
were dead. The effect on the other parts was as though the trees had been 
severely pruned. 
Colloidal Metals 
The solutions of the heavy metals proved detrimental to the normal 
growth of the trees. The colloidal metallic solutions were exceptions. 
Examination of the injected trees indicated that most of the injected colloids 
stayed in the trunks near the place of injection. 
Carbon Compounds 
Two of the carbon compound solutions proved very toxic when injected. 
Four-tenths percent formaldehyde^ affected the trees much as did the 
stronger concentrations of the copper solutions, but more severely for the 
reason that formaldehyde made broader paths when passing up the trunks. 
The trees above the point of injection were dead the following spring, but 
produced suckers from the base of the tree and from buds near the base. 
* Schering. 
