60 LIVING PLANTS 



mission is not hindered and a stem may be so 

 treated as to consist of alternate dead and 

 living portions and still transmit the effects 

 of stimulation. This set of experiments dispos- 

 es of the idea that the transmission of impulses 

 is in any sense a function of living matter in 

 mimosa. 



The presence of a system of elongated cylin- 

 drical cells in the outer part of the vsroody tis- 

 sue, containing glucosides and water under 

 pressure, led to the formulation of the theory 

 that these tubes were the paths of transmis- 

 sion and that impulses consisted of simple hy- 

 drostatic disturbances traversing the system, 

 as the pulsations of the forcing engines are 

 transmitted through the mains and pipes of a 

 city water system. 



The mere presence of these tubes can have 

 no especial significance, because they are found 

 in hundreds of species of Leguminosae in which 

 transmission does not occur. It is to be ad- 

 mitted of course that the tubes might serve 

 such use in mimosa, though not in any other 

 plant. When sudden disturbances are induced 

 in the contents of the tubes by means of 

 powerful pumps, abrupt pressure, the appli- 

 cation of heated rods to the stem or strong 

 chemical solutions to cut surfaces, no reac- 

 tions follow, and it is difficult in face of such 

 results to maintain that an impulse is a hy- 



