Dec. 18,1916 Influence of Bordeaux Mixture on Transpiration 
53i 
It is, of course, not possible in experiments of this nature to subject 
each leaf to precisely the same changes in aerial conditions. Special 
precautions were taken, however, to arrange the leaves involved in a 
single experiment in such a manner with reference to each other and to 
their surroundings that each might experience, as nearly as possible, the 
same changes in environmental conditions. This was accomplished by 
placing the flasks in rows 2 feet apart on a table centrally located in the 
greenhouse, where air currents from ventilators or open doors would 
affect the plants similarly. The arrangement decided upon for each 
experiment was maintained until the experiment was terminated. The 
leaves were removed from their positions only for the purpose of weighing, 
and each leaf was returned to the position previously occupied as soon as 
the weighing was completed. 
Each flask with its leaf (in series A and series B) was weighed to 0.01 
gm., allowed to stand for a definite time period, and again weighed. The 
difference between the two readings, of course, gave the absolute 
transpiration for the time period. The first period of exposure, before 
spraying the leaves of series A with Bordeaux mixture, may be regarded 
as the standardization period, and the leaves of the control series B may 
be regarded as the standard leaves for comparison. At the close of the 
standardization period the leaves of series A, which then became series 
A', were sprayed with Bordeaux mixture. This spray was prepared in 
the usual way and contained 12 gm. of copper sulphate and 12 gm. of 
lime in 1 liter of the mixture, approximating the 5-5-50 formula of 
agricultural practice. Both upper and lower surfaces of the leaves were 
sprayed, the spray being applied with an atomizer. This method yielded 
a very uniform film of spray over the leaf surfaces. 
A comparison of the ratios between the transpiration quantities of 
series A and those of series B for the time period before spraying with 
similar ratios for the time period after spraying will determine whether 
the transpiration rates of the leaves for the periods after spraying have 
changed. For the sake of convenience in the treatment of ratios, tran¬ 
spiration quantities for series A will be termed “A” for periods before 
treatment and “A'” for periods after treatment. The corresponding 
transpiration quantities for series B will be designated “B” throughout, 
since the leaves of series B were not treated with Bordeaux mixture. If 
then the ratio of A to B is greater than the ratio of A' to B, it follows that 
the rates of transpiration of the sprayed leaves have suffered a decrease 
relative to the rates of the unsprayed leaves. If, however, the ratio of 
A to B is less than the ratio of A' to B, then the rates of transpiration of the 
sprayed leaves have increased, relative to the rates of the unspraved 
leaves. In making such comparisons it must be assumed, of course, that 
the ratio of A to B for successive time periods would remain unchanged if 
the leaves of series A were not treated. It could scarcely be expected 
that the ratio of A to B would remain constant for successive intervals, since 
St is not possible to subject all the leaves to precisely the same changes in 
