REPORT OF THE SECRETARY 



113 



rate of respiration) until a state of equilibrium with the new environ- 

 ment is attained. If this phenomenon is of widespread occurrence 

 in green plants as well, it must be of considerable importance also 

 in experiments in which rates of photosynthesis are measured. 



Considerable time has been spent during the late winter and spring 

 in improving the performance of the spectrograph used in measuring 

 carbon dioxide, for very short periods. A 15-cc. volume absorp- 



lOO 



30 



^ 60 



^ 40 



20 



CONDITJONeo 

 iN 



FOR 

 /7.5 HRS. 





I 





I 



cOi f=K£e 



A I PL 





I 





r 



9 /O II 

 A.M. 



12 



4 S 

 P.M. 



r/M£ 



Figure 2. 



-Effect of previous CO2 environmental conditions on succeeding rates of respira- 

 tion of etiolated barley seedlings. 



tion cell providing a 15-cm. optical path was made in the shop and 

 installed on the instrument. The spectrograph case was lagged 

 with 4 inches of rock wool and the whole room thermostated to 

 maintain a temperature of 30° C. These features have improved the 

 speed-sensitivity and stability of the set-up very materially. The 

 assembly has been used recently in measuring the solubility of CO2 

 in water at very low concentrations where a marked departure from 

 Henry's Law was discovered. Further experiments on this are 

 in progress and will be published soon along with a detailed descrip- 

 tion of the spectrographic method of CO2 measurement. 



