THE 



CAUSES OF FLUCTUATIONS IN TURGESCENOE 



IN THK 



MOTOR ORGANS OF LEAVES. 



INTRODUCTION 



The following pages contain an attempt to demonstrate that the great majority, 

 if not all, of the transient spontaneous movements of higher vegetable organisms, 

 whether of a nyctitropic character or arising in connection with other conditions 

 than the incidence or removal of sunlight, are not dependent on the presence of any 

 specially irritable and contractile protoplasts within the motor organs, but on purely 

 physical processes connected either with fluctuations in the osmotic capacities of the 

 tissue-elements, or with alterations in the relations existing between local or general 

 supply and loss of water. This may at first sight appear to be a retrograde view, 

 but, at the same time, I feel assured that it is more in accord both with actual 

 fact and with evolutionary doctrine than that which is commonly accepted in Europe, 

 at the present time, and it is one which I have arrived at only after more than ten 

 years of almost continuous study of the subject. 



Conspicuous examples of transient spontaneous movements are relatively rare in 

 plants in Europe, and have therefore, to a great extent, been studied there in 

 connection with tropical plants growing under very abnormal conditions. This has 

 not unnaturally given rise, on the one hand, to an over-estimate of their exceptional 

 character, and, on the other, to imperfect and erroneous conceptions in regard to the 

 conditions under which they normally manifest themselves. But within the tropics 

 such movements, and specially those of a nyctitropic character, are so widely diffused 

 that they may readily be made the subject of continuous observation under normal 

 conditions, and with this the tendency to ascribe them to exceptional causes is 

 proportionately diminished. 



Observers in Europe unquestionably have many great advantages: the climate is 

 favourable to strenuous work; they possess very great advantages in regard to the 

 ready acquisition of special apparatus, and they can constantly avail themselves of 

 skilled criticism of any conclusions at which they may arrive. But, at the same 



