50 
CAROLINE RUMBOLD 
leaves a finely checked appearance. The parenchyma browned last. The 
leaves then became dry and curled upward. There was another kind of 
discoloration characteristic of these solutions which appeared on leaves 
distant from the point of injection, or at a point where the solutions injected 
were diluted. Irregular brown spots appeared on the edges of the leaves 
which spread gradually toward the green petiole. The line of demarcation 
between brown and green areas was sharply defined. Such leaves were 
found on all trees injected with heavy metals. This effect in turn was 
quite different from that produced on leaves in the uninjected parts of 
trees treated with concentrated solutions, where a gradual bleaching 
appeared. 
The manner in which formaldehyde 4/10 percent and meta-cresol 
i/iooo G.M. affected leaves has been described. While meta-cresol proved 
so toxic, para-cresol i/iooo G.M. produced no apparent effect on the leaves. 
Those carbon-compound-injected trees which had discolored leaves 
showed two variations of discoloration. Para-nitro-phenol 1/500 G.M. 
browned the midribs and veins of leaves near the point of injection. Those 
leaves gathered from more distant parts showed light brown blotches on 
the edges which gradually advanced toward the base of the leaf. (The 
leaves, as far as appearance was concerned, could have been taken from a 
tree injected with HgC^ i/iooo G.M.) Trees injected with the i/iooo 
G.M. solution of para-nitro-phenol also showed these two varieties of 
discolored leaves. Ortho-nitro-phenol i/iooo G.M. produced effects on 
leaves resembling those on ammonium-sulphate-injected trees, the leaves 
having translucent, brittle, frilled edges. 
Picric acid i/iooo G.M. caused the appearance of blotched and frilled 
leaves; citric acid 1/50 G.M., of blotched leaves; citric acid 1/500 G.M., of 
blotched and frilled leaves; acetic acid 1/500 G.M., of blotched leaves; 
formic acid i/iooo G.M., of blotched leaves; salicylic acid 1/5000 G.M., 
of blotched and frilled leaves; pyrogallic acid i/iooo G.M., of blotched 
leaves, the entire leaf finally turning a bright yellow and dropping off, as 
well as of frilled leaves; phloroglucine i/iooo G.M., of frilled leaves; 
pyrocatechin i/iooo G.M., of frilled leaves. 
A possible explanation for these three variations in the discoloration 
of the leaves on an injected tree is that the leaves became impregnated in 
the course of the solution's spread with varying dilutions of the injected 
substance, those at a distance being impregnated with a much more dilute 
solution than those near the place of injection. The more concentrated 
solutions killed the tissues as they passed, thus browning the midribs and 
veins of the leaves, leaving the parenchyma green. When sufficiently 
dilute they flowed into the leaves without apparent harm, but gradually 
accumulated through transpiration in the parenchyma cells until a poisonous 
effect was produced. The third variation, that in which the leaf edges 
wrinkled or frilled, may be the effect not of the substance originally injected, 
