THE FEELINGS OF PLANTS 107 



together, and the leaf-stalks to collapse. The 

 most singular feature is that the shock may be 

 communicated to other parts of the plant, and 

 even, at times, to the whole specimen. The 

 Sensitive Plant has something which is strangely 

 like a rudimentary nervous system, in that it 

 would seem that there is a continuity of suscep- 

 tible matter throughout the whole specimen. 

 There is little doubt that the contractile power 

 resides in small cylindrical cushions pulvini 

 which occur at the points of insertion of the 

 leaf-stalk with the stem. 



A pulvinus is a process containing a woody 

 centre surrounded by spongy cells rich in water. 

 Now, when one of the leaflets of the Sensitive Plant 

 is touched, the effect is transmitted, probably by 

 the threads of protoplasm passing through the 

 cell wall, to the pulvinus. The outcome of the 

 reception of the shock is that the water passes 

 from the cells on the lower side of the process 

 to those in the upper part, and, as a conse- 

 quence, the former portion becomes flabby and is 

 no longer able to support the leaf-stalk. Thus 

 the organ falls by its own weight. After an 

 interval the water in the cells regains its original 

 distribution and the leaf assumes its normal 

 position. 



