14 THE BOTANICAL MAGAZINE. LVoi. xxxiv. No. 397. 



Plant physiologists frequently have to deal with the time 

 relations of natural processes that are related to sunrise", sun- 

 set, etc. ; e. g., we study the daily march of the transpiration 

 or photosynthesis of the plant. An artificial time schedule is 

 often used without the realization that difficulties are intro- 

 duced. It would be better if sun time were used in such cases. 



Solar time is easily determined by the use of the primitive 

 sun-dial, and an investigator's watch may be set by that 

 instrument. A simplar way to make time records in terms of 

 solar time would be for the investigator to leave his watch set 

 for standard time and to correct his notes according to the 

 constant difference between sun time aud standard time. Thus, 

 if his standard time is 20 minutes ahead of the solar time of 

 his station, he would be substract 20 minutes from each time 

 record, thus translating it from standard into solar time. 



Attention to this matter might save considerable trouble in 

 connection with detailed studies of daily fluctuations in physio- 

 logical processes and in environmental conditions. 



The Johns Hopkins University, 

 Baltimore, Md. U. S. A. 



