ACTION OF THE NERVOUS SYSTEM. 71 



and the pistil left, then nutation goes on as usual. 

 But beyond this, if the ovules are extirpated, but 

 the wall of the ovary left standing, the nutation is 

 stopped. Hence we arrive at the striking conclu- 

 sion that the presence of developing ovules in the 

 young ovary determines the reaction of the flower- 

 stalk towards gravity." 



In these two experiments, we see that the destruc- 

 tion of a part of a plant changes that co-ordination 

 of forces which produces the growth and controls 

 the movement of the growing parts. When we 

 see the effects of a local injury made apparent in 

 a distant part of the plant, we must believe the 

 living part of the plant to be capable of some action 

 like nervous conductivity. And when we see that 

 the manner of growth and movement is in part 

 dependent upon some localised centre, we are 

 further led to the belief that the co-ordinations of 

 forces in the plant are similar to the nervous co- 

 ordinations which control the functions of animals. 



Other experiments show more clearly the nervous 

 nature of the co-ordinations controlling the activities 

 of plants. They show not only how these co- 

 ordinations in the protoplasm of the plant react to 

 the external forces, but also how the reaction 

 becomes by repetition ingrained in the living matter 

 of the plant, so that for a limited time after the 



