TIIK TLANT AS A MACHINK 



7 



action of different influences, can be made visible to the 

 whole audience. It is thus possible to obtain records of these 

 pulsatory movements, by attaching; the Optical Lever to the 

 leaflet of an intact plant. Or wc may detach a petiole, 



Fig. 4. Demonstration Optica) Pulse- Recorder 

 B, Arm of Optical Lever, attached to moving leaflet ; L, Ray of light, which 

 after two reflections from the two mirrors falls on the recorder ; c, Clock, 

 which keeps twin-drum— on which is wrapped the recording paper — 

 revolving ; n. Horizontal guide-bar ; K, Ink-well, with projecting 

 sponge. 



carrying the leaf, and place it in water, in which case it 

 will remain alive as long as a couple of days, executing its 

 accustomed pulsatory movements during a considerable time. 

 The effect of any given agency, say poison, on the living 



