1918] BAKKE—WILTING ‘ 99 
cases when the evaporation was at its highest. This part of the 
graph conforms with the one obtained when the plants were lifted 
from the soil. On August 7 the index of foliar transpiring power 
increases from 0.13 to 0.23, or 77 per cent from the roth hour to 
the 14th hour. On the previous day it dropped from 0.14 to 0.11, 
while on the preceding day the two indices were the same. At no 
other time during the march was there such a great percentage 
increase. 
In obtaining the ratio between the day reading and the night 
reading for 24 consecutive hours, the day readings were usually 
made between the oth and the roth hours. For the night readings 
there was no need of selection as only one reading was taken. 
Beginning with July 24, and continuing until July 29 (time of 
wilting), the transpiring power indices representing the day read- 
ings for Ia, are 0.51, 0.49, 0.51, 0.43, 0.38, 0.33, while the 
corresponding night values are 0.28, 0.59, 0.49, 0.69, 0.36, 0.33. 
The respective ratio values are 1.82, 0.53, 3.04; 0:62, 2/05. On 
July 21-22 the ratio between the reading on the oth hour and the 
reading on the 21st hour is 0.88:0.52, or 1.7. For the entire 
24-hour period the maximum and minimum ratio is 1.9. The 
only normal ratio is the first. It is interesting to note that for leaf 
Ia, the minimum is normally 0.50. During the progress of wilting 
the maximum does .not get below this point until July 27; ‘after 
that it is below the usual minimum. 
From July 24 to August 7 (time of wilting) the corresponding 
indices for Ia, are present; for the morning 0.68, 0.29, 0.31, 0.20, 
0.16, 0.18, 0.21, 0.34, 0.17, 0.14, 0.14, 0.17, 0.17, 0.14, 0.13; 
for the night 0.39, 0.31, 0.21, 0.18, 0.19, 0.13, 0.16, 0.09, 0.13, 
0.16, 0.16, 0.17, 0.11, 0.13. The ratio of the day (morning) 
readings to the night readings is respectively 1.74, 0.94, I-11, 
0:04, 1.38, 1.3%, 3.78, 1.31; 6.88, 0:88, t.00, 1.54, 1.08. For 
July 21-22 the ratio of maximum to minimum for Ia, is 1.72. For 
the corresponding hours the ratio is 0.95:0.66, or 1.44. On this 
basis, therefore, the readings of the first day are normal, in that 
the ratio is approximately the same as for the maximum to the 
Minimum on July 21-22 (1.72). Also the maximum values during 
the march of wilting, with the exception of the first reading, are all 
