20 



BURTON EDWARD LIVINGSTON 



niination. No two consecutive determinations were made upon the 

 same plant. From four to eight tests were made in each case, 

 the results being averaged for each of the two leaf surfaces. The 

 water test was carried out hourly, in a similar way, and the results 

 averaged. The time required for the color response of the 

 hygrometric paper over the standard water surface varied from 

 18 sec. (hours 11 to 13) to 27 seconds (hours 1 to 4). The 

 experiment began at 11 hours, September 2, 1911, and ended at 

 14 hours, the day following. The day was almost entirely clear, 

 with very few light clouds.. Dawn occurred about 4 hours and 

 sunrise about 5 hours. 



Table 4 presents the indices of transpiring power for the upper 

 and lower foliar surfaces, for the end of each indicated hour, as 

 well as for the hour period preceding, these indices being derived 

 quite as in experiment I. The table also includes the averages of 

 the upper and lower indices for the hour periods, these averages 

 being taken to represent the condition of the entire leaf surface 

 as to its transpiring power. They are, therefore, more or less 

 comparable to the corresponding relative transpiration ratios. 

 The three different series are also given in the reduced form, the 

 reduction being so made in this instance as to relate each index 

 to the lowest one of the series as unity. It will be noticed that 

 this method does not necessarily bring unity in the reduced series 

 to the same hour, as does the method resorted to in experiment I. 

 The numbers have all been rounded off with the third place of 

 decimals for the primary series and with the first place for the 

 final reduced series in each case. The rounding off was not per- 

 formed, however, until after the various necessary operations 

 had been accomplished; the accuracy of our figures is far greater 

 than is requisite in such studies as this. The data for the entire 

 leaf surface at the ends of the hours have been omitted from this 

 table ; they are readily to be obtained by averaging the correspond- 

 ing numbers in columns 2 and 5. The items of column 8 have 

 been derived by averaging the corresponding ones of column 3 

 and 6. 



In general character, the data of table 4 agree with those of 

 table 2. Here, as in the former experiment, the range of tran- 



