86 JOHN W. SHIVE AND WILLIAM H. MARTIN 



and it is here suggested that the method is equally applicable 

 to similar studies involving the use of other spray materials. 

 The method may also be found useful for the investigation of 

 the transpiring power of diseased plants, or of diseased plant 

 parts: a matter of considerable importance in coim.ection with 

 certain pathological, as well as physiological studies. 



For each single day, the average values of the indices of trans- 

 piring power of the leaves treated with films of Bordeaux mix- 

 ture may be considered to be roughly proportional to the cor- 

 responding values of the untreated leaves of the same and of 

 different plants. 



The indices of transpiring power of the treated leaves, for 

 August 14 and 18, show values averaging 23% and 21% higher, 

 respectively, than the corresponding index values of the un- 

 treated leaves of the same plant. In like manner, the index 

 values of the treated leaves, for August 10, 14, and 18, average 

 25%, 29%, and 18%, higher, respectively, than do the corre- 

 sponding indices of the leaves of the untreated plants. 



The graphs showing the march of foliar transpiring power, 

 indicate that the maximum indices occur near the middle of 

 the day. The graphs of each single set, representing the index 

 values of the three groups of leaves here considered, all agree 

 in indicating their maxima at the same hour of the day, although 

 the ma,xima of the three different sets of graphs occur at differ- 

 ent hours on different days. 



The influence of Bordeaux mixture effective in producing 

 higher indices of transpiring power, of the plants here employed, 

 under the particular sets of conditions prevaihng when the 

 tests were made, is just as effective when these indices are low 

 as it is when they are high. 



