New YorK AGRICULTURAL EXPERIMENT STATION. 239 
it is reasonable to assume that some of the changes in the cellular 
structure are due to healing processes since it is known that irrita- 
tions of many kinds, as rubbing against a branch, heal similarly in 
many tree fruits. It seems certain, as will be shown later on, that 
the toxic substance in the bordeaux mixture combines with the 
cell contents and is stored up in the dead cells, and that the poison- 
ing or corrosion, as the case may be, does not spread from cell to 
cell; only the cells in which the toxic compound enters are affected. 
The amount of injury varies greatly with: (1) The structure 
of the skin (there is great variation in the skins of apples of 
different varieties). (2) The condition of the skin as to the age of 
fruit and the succulency or tenderness from weather conditions. 
(3) It is not improbable that the chemical constituents of the cell 
juices may hinder the toxic action of the bordeaux mixture in some 
varieties, thus in part accounting for comparative immunity. 
This brief study of the skin of the apple under normal and the 
diseased conditions indicates why we should expect injured fruits 
to keep poorly. The skin is the protective organ. When wholly 
or partially destroyed, as in bordeaux injury, the doors are open 
for the escape of moisture through evaporation and for the en- 
trance of the germs of decay. 
RORDEAUX INJURY OF THE FOLIAGE. 
On the foliage bordeaux injury very greatly resembles the leaf 
spot supposed to be caused by any one of several fungi. The 
affected leaves first show dead, brown spots; the majority of these 
spots are circular or roundish with a diameter of two.or three 
millimeters, but they may be of various shapes and sizes; many 
are of irregular outline and so large as to appear to have been 
caused by the coalescing of smaller spots. The line of demarca- 
tion between the dead tissue of the spots and the living green of 
the leaf is well marked so that the spots are very conspicuous. 
Quickly following the appearance of the brown spots the remain- 
ing tissues begin to turn yellow and this usually continues until 
the living tissue is of a yellowish color when the leaves fall, the 
petioles breaking from the stem as in natural falling. When the 
injury is slight the yellowing may not appear, in which case the 
leaves do not drop. In general, the injury on the leaves of all 
varieties, so far as I have been able to observe, is of the same 
character. 
