200 LIFE AND WORK OF SIR JAGADIS C. ROSE 



Bose's investigation on the ' Praying Palm ' is thus 

 enunciated : 



For obtaining an explanation of the phenomenon it was 

 necessary : 



1. To obtain an accurate record of the movement of the 

 tree day and night, and to determine the time of its maximum 

 erection and fall. 



2. To find whether this particular instance of movement 

 was unique, or whether the phenomenon was universal. 



3. To discover the cause of the periodic movement of the tree. 



4. To determine the relative effects of light and temperature 

 on the movement. 



5. To demonstrate the physiological character of the move- 

 ment of the tree. 



6. To discover the physiological factor whose variation 

 determines the directive movement. 



For the details of this inquiry, the original paper must be 

 referred to : enough here to summarise the main results- 

 The curve recording the ' prostration ' of the tree towards 

 evening, with its nightly rise anew, very closely corresponds 

 to that of the daily rise and nightly fall of temperature, 

 though naturally lagging a little behind. This the reader 

 will see on comparing the curves, which represent the 

 variation of temperature and the movement of the 

 palm (Fig. 25). Investigation on a younger and less 

 bent palm of the same species growing in Bose's garden, 

 down-stream from Calcutta, 200 miles from Faridpur, 

 showed an even more exact correspondence of the tree's 

 movements with the temperature changes, the more since 

 this smaller tree admitted of the erection of a tent over 

 it during its observation, so as to prevent wind from 

 disturbing the record, and also to mitigate any possible 

 effect of the alternation of sunlight with darkness. 



The objection next arises May not this diurnal 

 rhythm be but a physical effect of temperature, not a 

 physiological one ? The question, however, was finally 

 settled by the unfortunate death of the tree, which took 

 place a year after the commencement of the investigation. 



