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THE AMERICAN NATURALIST [Vol. XLIII 



growth. He was not indeed the first to observe individ- 

 ual instances of either periodic or ephemeral movements 

 of a more or less pronounced degree, but to him belongs 

 the credit of first insisting upon the fact that all growing 

 organs describe a more or less spiral orbit. He de- 

 veloped this idea with such enthusiasm that he carried 

 his line of thought to extremes and concluded that all 

 plant movements were but modifications and adaptations 

 of circumnutatory motions. Only in the cases of the 

 motions of Mimosa leaves and Drosera. tentacles did he 

 express his doubt as to the applicability of the principle 

 of circumnutation to all plant movements. He included 

 all forms of tropisms, contact responses, other than those 

 named, under this one head. In the final chapter of 1 1 The 

 Power of Movement in Plants" he says: 



It has been shown that the following classes of movement all arise 

 from modified circumnutation, which is omnipresent whilst growth 

 lasts, and after growth has ceased, whenever pulvini are present. 

 These classes of movement consist of those due to epinasty and hypo- 

 nasty,— those proper to climbing plants, commonly called revolving 

 nutation, the nyctitropic or sleep movements of leaves and cotyledons, 

 and the two immense classes of movement excited by light and gravi- 



In the next paragraph he excepts the contact move- 

 ments of Mimosa and Drosera, already referred to, 

 saying: 



Although so many movements have arisen through modified circum- 

 nutation, there are others which appear to have a quite independent 

 origin; but they do not form large or important classes. 



When we consider the nature of the man and reflect 

 that the whole trend of his mind was towards the concept 

 of unity in the organic world it does not seem extraordi- 

 nary that he should have taken such an attitude; an 

 attitude too that was helped on by the extreme simplicity 

 of his methods of experimentation. The very fact that he 

 approached the question with a mind entirely free from 

 bias had its advantages, but it also brought a greater 

 chance of being too easily swayed by his own point of 

 view. It must be remembered also that the distinction be- 



