TRANSPIRATION UNDER CONTROLLED CONDITIONS. 



59 



a lessening in the rate of decrease but not by an actual increase. The occur- 

 rence of the maxima of actual and of relative transpiration was 4 and 6 

 hours, respectively, before the time of maximum evaporation for the day. 

 No. 7 behaved differently in that its maximum of actual transpiration coin- 

 cided with the maximum for evaporation and no tendency toward a break 

 in the acceleration appeared. The maximum for relative transpiration 

 occurred four hours earlier than the transpiration maximum, and while a 



Tabi-e 24. Transjriralion under three different evaporation conditions. Experiment XXI. 



drop and rise occur in these rates it will be seen from a comparison with 

 the transpiration and evaporation rates that they are caused by a decrease 

 in the evaporation rate which is not followed by the plant, and hence that 

 this dip and rise are in no sense the kind under investigation in this paper. 

 The intermittent cloudiness of April 2 made it advisable to repeat the 

 experiment on a clear day, and consequently this was done on April 4. 



