532 
Journal of Agricultural Research 
Vol. VII, No. 12 
aerial conditions. Furthermore, internal changes continually takingplace 
in the leaves would tend to cause some variations in the ratio of A to B, 
since the degree of these changes would certainly vary from leaf to leaf, 
even supposing the nature of these changes to be the same in all the 
leaves. It may reasonably be supposed, however, that variations in the 
ratio of A to B for successive intervals, due to internal changes and to 
differences in the changes of environmental conditions experienced by 
the different leaves of a series, are comparatively small. This was, 
indeed, found to be the case in a series of preliminary experiments. The 
time peiiod during which an experiment may be conducted with relatively 
very small variations in the ratio of A to B, owing to conditions other than 
the treatment with spray, varies, of course, with the different species. 
Experimental results. —The experimental data showing the effect 
of Bordeaux mixture on the transpiration of abscised leaves are pre¬ 
sented in Table I. The first column of this table gives the names of the 
various species dealt with and the time at the beginning and end of 
each experimental period. This is followed, under “ Periods before treat¬ 
ment,' # by three columns giving transpiration quantities, in grams, of 
the three leaves of series A; then are given three columns presenting 
transpiration data for series B for the same time periods. The last 
column of this section gives ratios obtained by summing the values of 
the transpiration quantities of the three leaves (on the same horizontal 
line) of series A and dividing this summed value by the summed value 
of the corresponding transpiration quantities for series B. The second 
section, under “Periods after treatment," presents in the same way as 
the first the data comparing series A' with series B. The table is further 
divided into a number of horizontal sections, each section presenting all 
of the data for a single species. 
The data included in the first horizontal section of Table I represent 
an experiment extending over a total time period of more than five days. 
The transpiration data for datura leaves presented in the second hori¬ 
zontal section of the table represent an experiment extending over a 
total time period of more than four days. During these two experiments 
weighings were made each day, as indicated. The data presented in the 
remaining sections of the table represent experiments conducted mainly 
to determine whether the spray becomes effective in its influence on 
transpiration, immediately after drying on the leaves, or whether modified 
rates of water loss begin at some later period. All of these experiments 
were conducted during the same day, extending over a total time period 
of a little more than io hours. Water loss from each leaf was determined 
at intervals of two hours. The containers used in these experiments 
were small, so that weighings could be made to o.oi gm. At the end of 
the two standardization periods the leaves of the A series were sprayed 
on the upper and lower foliar surfaces, and weighings were made soon 
after the spray had completely dried on the leaves. 
