

VARIOUS MOVEMENTS IN PLANTS 167 



to its necessary technical and logical minimum, without 

 impairing sufficiency. 



There are so many cases and kinds of plant-movements 

 that terms have gone on multiplying far faster than the 

 understanding of them. True, despite all this superficial 

 nomenclature, and by the very authors of it, there have 

 been many experimental endeavours to elucidate and 

 interpret the real causes underlying these phenomena, 

 i.e. to observe and measure the effects of various stimuli, 

 as of light and others. Yet the terminology employed 

 is not only redundant, but often wrong. And though 

 Pfeffer summarises the literature of the subject up to 

 the coming of Bose, and often with research and inter- 

 pretation of his own, and uses these terms with 

 moderation, since after all they do help to group the obvious 

 phenomena, he so far sees their limitations. For the 

 terms employed give no explanation of the phenomena 

 they are used to connote. 



' When we say that an organ curves towards a source 

 of illumination because of its heliotropic irritability, we 

 are simply stating an ascertained fact in a conveniently 

 abbreviated form without explaining why such curvature 

 is possible, or how it is produced/ 1 



The weakness of the situation is recognised by 

 Pfeffer's clear-headed translator, Professor Alfred Ewart, 

 who also protests against this excess of names, and with 

 the needed general criticism : ' Error lies in supposing that 

 a dissimilar response necessarily indicates a totally distinct 

 form of irritability, and hence needs a new term, or that 

 phenomena are made simpler or easier to understand by 

 giving them a classical terminology/ 



Great uncertainty thus prevails as regards the explana- 

 tion of various movements of plants. Hence the need for 

 Bose's thoroughgoing reinvestigation of the phenomena ; 

 and these now taken in relation with the sensitiveness to 



1 H. Pfeffer, Vegetable Physiology (Clarendon Press), 1903, ii. 74. 



