84 JOHN W. SHIVE AND WILLIAM H. MARTIN 



unsprayed leaves of the same plant (series B) and for the leaves 

 of the unsprayed plant (series C), respectively. 



Inspection of the graphs shows that the index values for the 

 sprayed leaves are, with only one exception, greater than are 

 the corresponding values for the unsprayed leaves, whether on 

 the same plant or on a different plant. The single exception, 

 to which reference has already been made, is given for the seventh 

 hour, August 14. Here the index value for the leaves of the 

 unsprayed plant (series C) is slightly higher than the corre- 

 sponding value for the sprayed leaves. 



The various graphs show slight irregularities, . but there is 

 a marked tendency for the same irregularities to occur at cor- 

 responding points on the three graphs (two for August 10) of 

 a set. This is particularly striking for the graphs representing 

 the indices for the sprayed and unsprayed leaves of the same 

 plant. The three sets of graphs show clearly that the foliar 

 transpiring power, as measured by the method of standardized 

 hygrometric paper, rises to its maximum about the middle of 

 the day, falls somewhat abruptly for several hours, and then 

 more slowly to the low values attained late in the day. It will 

 be observed that the maximum index values for the three sets 

 of graphs are here indicated at different hours of the day, but 

 the maximum for each graph of a single set appears at the same 

 hour. The maximmn transpiring power of the leaves of each 

 series on August 10 was attained at the thirteenth hour. The 

 maxima for August 14 and for August 18 were reached at the 

 eleventh hour and the twelfth hour, respectively. 



It is to be noted that the indices for entire leaf surfaces of 

 series A and series C, on August 10, are, with only one exception, 

 much higher in value than are the corresponding indices on 

 either of the other two days. This striking difference in the 

 values of corresponding indices is not at once made apparent 

 from a casual inspection of the graphs, since the graphs of in- 

 dices for August 10 are plotted on a different scale than are those 

 for the other two days. The difference here indicated may be 

 due to the fact that for several days preceding August 10, a 

 rainy season prevailed, so that the moisture content of the soil 



