THE PLANT AS A MACHINE 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 we may detach a petiole, 



Fig. 4. Demonstration Optical 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 ; H, 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 



