Jan., 1920] Resistance of Leaves to Transpiration 



m 



experiments were performed in the greenhouse was obtained 

 from the U. S. Weather Bureau Station, Columbus, Ohio. 

 This record is expressed in percentages of possible sunshine per 

 hour. No record of wind velocity was kept except in the 

 experiments when an electric fan was used to produce air 

 currents. Then a U. S. Weather Bureau anemofneter was 

 used and the velocity is expressed in miles per hour. 



Fig. 2. 

 One of the plants used in the experiments, showing the method of sealing and 



irrigating the pot. 



The evaporation and transpiration records were determined 

 as described by Transeau by replacing the loss of weight of a 

 plant or atmometer, which is balanced on one pan of a balance, 

 by dropping steel shot each weighing a gram on the pan beside 

 the plant and recording the number of shot required to keep 

 the plant balanced, with the time interval between shot. 



