SOIL MOISTURE AND TO EVAPORATION. 



55 



manner as that used in the previous experiment, in figure 10. As in 

 Experiments I and IV, a periodic fluctuation in the rate of relative trans- 

 piration is shown, the low period being in the night and the high 

 period in the day. During the record of the experiment only a single 

 unquestionable maximum is shown. This has a rate of relative trans- 

 piration of 0.237 at 6 h 30 ra a.m., and occurs with a temperature of 79 F. 



FIG. 10. Curve of relative transpiration for a second plant of Tribulus, 

 August 13-15, 1904. 



and an evaporation rate of 0.013 gram. Two minima are shown on the 

 curve, one indeterminate from the curve's form, but probably to be 

 considered as in the vicinity of 9 h 30 ra p.m., with a relative transpiration 

 rate of 0.038, a temperature of 75 F., and an evaporation rate of 

 0.012 gram, the other at 9 p.m., with relative transpiration rate of 

 0.029, temperature of 79 F., and evaporation rate of 0.026 gram. It is 

 to be noticed that in the night of August 13-14- the minimum tern- 



