12 



BURTON EDWARD LIVINGSTON 



In the presentation below, all of the original data will not be 

 given, selected samples being allowed to indicate the methods 

 of manipulation and calculation to which the original obser^'a- 

 tions have been subjected. 



Experiment I. This series of observations brings out the abso- 

 lute values and the range of variation in transpirational retarda- 

 tion for a single species under the conditions of the experiment, 

 and also makes possible a direct comparison of results obtained 

 by means of the method of cobalt chloride paper with other results 

 derived through the relative transpiration ratio. The series was 

 carried out with potted plants Physalis angulata L. var. linkiana 

 Gray, a plant that occurs plentifully in the experiment grounds 

 of the Desert Laboratory, developing vigorously and producing 

 flowers and fruit in the season of the summer rains. The experi- 

 ment continued from 21 hours of July 25 to 12 hours of the fol- 

 lowing day. At 11 hours 35 minutes, the series was interrupted 

 by a heavy shower, which necessitated the removal of the plants 

 and instruments into the laboratory. 



Two observations with cobalt chloride paper were made hourly, 

 for the upper and for the lower leaf surface, the water test (with 

 free water surface) being also made. Two plants were used, the 

 tests being made with leaves of medium age. Different leaves 

 were employed for consecutive hours. The plants were taken 

 into the laboratory for the paper test and returned to the open 

 as soon as this was completed. 



Hourly readings of a white atmometer and of a brown radio- 

 atmometer,^ — both instruments drawing water from burettes, — • 

 were obtained, also hourly weighings of two sealed potted plants, 

 and the relative transpiration ratios were derived according to 

 the methods described in Publication 50 of the Carnegie Institu- 

 tion. The atmometers were both placed in the incUned position, to 

 make the angle of incidence of the sun's rays upon the cup approxi- 

 mately constant throughout the day. The instruments remained 

 in the open until 1 1 hours 30 minutes, the plants were taken into 



' Livingston, B. E., A radio-atmometer for measuring light intensities. Plant 

 World, 14:96-99, 1911. 

 Idem. Light intensity and transpiration. Bot. Gaz., 62: 418-438, 1911. 



