SIJBARIA PALM 23I 



(2) by the locality, whether it is exposed or shaded ; (3) by 

 the condition of the weather ; and (4) by the radiation of heat 

 from the ground. It varies according to circumstances 

 from I to 3 P.M. The thermal dawn, generally speaking, is 

 shortly after sunrise. The movement of the tree lagged 

 somewhat behind the change of temperature ; erection 

 commenced after the thermal noon, and the fall began 

 after the thermal dawn. 



The Periodic Movement of Sijbaria Palm 



Another question which had to be investigated was 

 whether the movement of the Faridpore Palm was a unique 

 phenomenon, or whether other Date Palms exhibited similar 

 movements. With this end in view, I experimented with 

 a Date Palm that was growing at my Research Station at 

 Sijbaria on the Ganges, situated at a distance of 200 miles 

 from Faridpore. 



Experiment 127. — The surrounding conditions wxre 

 very different ; the tree itself was much younger and w^as 

 at an inclination of 20° to the vertical instead of 60° as in 

 the previous case. The tree w^as enclosed in a dark tent to 

 exclude the action of hght. The diurnal curve of its move- 

 ment was found to be very similar to that of the Faridpore 

 Palm, though the extent of its movement was considerably 

 less. The tree attained its highest erect position at 7.15 a.m. 

 and the lowTst at 3.45 p.m. (fig. 135). In settled w^eather 

 the diurnal rise and fall of temperature is very regular, and 

 so was the movement of the tree. But under less settled 

 conditions, owing to change of direction of wind, the tem- 

 perature-curve exhibited fluctuation. It w^as a matter of 

 surprise that the plant-record should have repeated this 

 fluctuation with astonishing fidehty, as seen in the common 

 twitch in the two curves shortly after 8 a.m. There can, 

 therefore, be no doubt whatever about the movement being 

 principally due to variation of temperature. 



The extent of the up and down movement of the Sijbaria 



