DIURNAL MOVEMENTS IN PLANTS o25 



the leaves, when illuminated from below, turned their 

 laminae downwards during the day, but during the night 

 became erect geotropically. The sleep movements in leaves 

 and flowers, referred to above, cannot however be explained 

 by assuming such a combination of heliotropism and 

 geotropism."* 



I commenced my investigation on nyctitropism five 

 years ago, after having perfected an apparatus for continu- 

 ous record of the movements of plants throughout day 

 and night. A contrivance, described further on, has been 

 devised for obtaining a record of diurnal variation of tem- 

 perature. I have also succeeded recently, in perfecting a 

 device for automatic record of variation of intensity of 

 light. It has thus been possible not only to obtain a 

 continuous reconl of the diurnal movement of the plant, 

 but also obtain stimultaneous record of those changes in 

 the environment which might have an influence on the 

 daily movement. I have in this way collected several 

 hundred autographs of different plants throughout all 

 seasons of the year. The records thus obtained were 

 extremely diverse, and it was at first impossible to discover 

 any fundamental reaction which would explain the pheno- 

 menon. While in this perplexity my attention was 

 directed two years ago to the extraordinary perform- 

 ances of the " Praying Palm " of Faridpore, in which the 

 geotropic curvature of the tree underwent an accentua- 

 tion during fall of temperature, and a diminution daring 

 rise of temperature. 



The discovery of this new phenomenon led me to the 

 inquiry whether Thermo-geotropic reaction, as I may call 

 it, was exerted only on Palm trees, or whether it was a 



* For further information on tlie subject of Nyctitropism, cf.— 

 FfeSer—lbid, Vol. I[ (1903), p. 112: 

 Jost— 76jrf, pp. 500, 507 ; 

 Vines— Physiology of Plants U88t>), pp. 406, 543. 



