PUBLICATIONS. 



79 



' Power of Movement in Plants.' This was a tough piece of 

 work. The book bears somewhat the same relation to my 

 little book on * Climbing Plants,' which ' Cross-Fertilisation ' 

 did to the ' Fertilisation of Orchids ; ' for 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 kinds of 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- 

 isation, viz. that the great and important classes of move- 

 ments, excited by light, the attraction of gravity, &c., are all. 

 modified forms of the fundamental movement of circumnuta- 

 tion. It has always pleased me to exalt plants in the scale of 

 organised beings ; and I therefore felt an especial pleasure in 

 showing how many and what admirably well adapted move- 

 ments the tip of a root possesses. 



I have now (May i, 1881) sent to the printers the MS. of 

 a little book on ' The Formation of Vegetable Mould, through 

 the Action of Worms.' This is a subject of but small im- 

 portance ; and I know not whether it will interest any readers,* 

 but it has interested me. It is the completion of a short 

 paper read before the Geological Society more than forty 

 years ago, and has revived old geological thoughts. 



I have now mentioned all the books which I have pub- 

 lished, and these have been the milestones in my life, so 

 that little remains to be said. I am not conscious of any 

 change in my mind during the last thirty years, excepting in 

 one point presently to be mentioned ; nor, indeed, could any 

 change have been expected unless one of general deterioration. 

 But my father lived to his eighty-third year with his mind as 

 lively as ever it was, and all his faculties undimmed ; and I 

 hope that I may die before my mind fails to a sensible ex- 

 tent. I think that I have become a little more skilful in 

 guessing right explanations and in devising experimental 



* Between November 1881 and Februaiy 1SS4, S500 copies have been 

 sold. 



