34 MOVEMENTS OF SEEDLINGS. 



IV. 



MOVEMENTS OF SEEDLINGS. 



THE tips of all young growing parts of the 

 higher plants continually revolve, bowing succes- 

 sively towards every point of the compass. Dar- 

 win calls this movement circumnutation. In the 

 introduction to his book/ " The Power of Move- 



1 " The Power of Movement in Plants " was published in 1880. 

 Darwin had previously published, in 1875, an essay on " Climbing 

 Plants," in which he had shown that the young tips of twining stems, 

 tendrils, leaf-stalks, etc., continually revolve, and that this movement 

 is the immediate cause of their twining. The later work extends this 

 conception to the tips of all young growing parts of plants. In his 

 autobiography, Darwin says, "In accordance with the principle of 

 evolution it was impossible to account for climbing plants having 

 been developed in so many widely different groups, unless all plants 

 possess some slight power of movement of an analogous kind. This I 

 proved to be the case, and I was further led to a rather wide general- 

 izationj viz., that the great and important classes of movements excited 

 by light, the attraction of gravity, etc., are all modified forms of the 

 fundamental movement of circumnutation. It has always pleased me 

 to exalt plants in the scale of organized beings ; and I therefore felt 

 an especial pleasure in showing how many and what admirably well 

 adapted movements the tip of a root possesses." 



The conclusions of this book have not been generally accepted, and 

 have met with much criticism, especially in Germanyo Francis Darwin 

 says ("Life and Letters of Charles Darwin," II. p. 502), "The central 

 idea of the book is, that the movements of plants in relation to light, 

 gravitation, etc., are modifications of a spontaneous tendency to revolve 



