XLIX.— DAILY MOVEMENT IN PLANTS DUE TO 

 THERMO-GEOTROPISM 



By 



Sir J. 0. BosE, 



Assisted bij 



Lalit Mohan Mukherji. 



Of the vast number of daily movements perhaps the 

 largest proportion is due to thermo-geotropic reaction and 

 its modifications. Thermo-geotropic movements Lave the 

 following characteristics : 



1. The organs are sensitive to the stimulus of gravity 

 and the periodic movements are brought about by varia- 

 tion of geotropic curvature under change of temperature. 



2. The movement is not confined to growing organs, 

 ])ut is also exhibited by organs which are fully grown and 

 even by rigid trees. 



3. The periodic movement is closely related to the 

 diurnal variation of temperature. Fall of temperature from 

 thermal-noon (about 2 p.m.) to thermal-dawn (about a.m.) 

 is attended by a movement of erection ; rise of temperature 

 from thermal-dawn to thermal-noon is followed, on the 

 other hand, by a reverse movement of fall. 



That the movement is primarily due to variation of 

 temperature will be demonstrated in two different ways : 



(cr) by the change of normal rhythm of movement by 

 artificial transpositions of periods of maximum 

 and minimum temperature, and 



(/>) by the abolition of periodic movement through 

 maintenance of constant temperature. 



