82 CHAP. X. THE ELECTRIC RESPONSE TO LIGHT 



Anaesthetics such as ether induce depression or aboli- 

 tion of the electric response. Excess of carbon dioxide 

 induces a depression or arrest of growth ; it also arrests 

 the pulsatory activity of the leaflet of Desmodium gyrans. 

 The electric response of Hydrilla is similarly depressed or 

 abolished by an excess of carbon dioxide. Photosynthesis 

 undergoes a parallel depression. 



