58 



The Ohio Journal of Science [Vol. XX, No. 3, 



EXPERIMENTAL METHODS. 



The experiments summarized in this paper were performed 

 under the direction of Dr. E. N. Transeau, at the Ohio State 

 University in the research room of the Botanical Greenhouse 

 and in a darkroom adjoining the Plant Physiology laboratory. 

 The apparatus, with some alterations, which was used has been 

 described by Transeau (9). 



Fig. 1. 



Rotating table with the apparatus and plants arranged on it. The table was 

 turned at a very slow rate during the experiments. 



In each of the experiments continuous, simultaneous, 

 records of the following factors were secured for a period of 

 24 hours or more; temperature, humidity, duration of sunshine, 

 intensity of sunshine (as shown by the increased evaporation 

 from a black atmometer compared with that from a white 

 atmometer), evaporation from a white atmometer cup, trans- 

 piration from one or more plants, and wind velocity. The 

 temperature was recorded in degrees, Fahrenheit, and the 

 humidity in percentages of saturation, on a combined hygro- 

 thermograph, which was checked up from time to time with a 

 standard sling psychrometer and corrected if necessary. A 

 record of the duration of sunshine for the days on which 



