62 CHAP. VIII. CHANGE IN PHOTOSYNTHETIC ACTIVITY 



Chloroform. — When the plant is placed in water mixed 

 with chloroform, the rate of bubbling becomes slowed down, 

 culminating in an arrest. This is a qualitative demonstra- 

 tion of the narcotic effect of 

 chloroform. For quantitative 

 determination, ether is pre- 

 ferable, for two reasons : first, 

 because the effect is gradual, and 

 second because it is possible to 

 obtain complete restoration after 

 removal of the anaesthetic. 



Ether. — Having ascertained 

 the normal rate of bubbling, the 

 usual C0 2 -solution with I per 

 cent, of ether added is intro- 

 duced into the plant-vessel. The 

 rate of bubbling is now found 

 to undergo a continuous decline 

 with the duration of applica- 

 tion. The normal period was 26 • 5 



, , 60 X 60 

 seconds, or an activity of — ^ 



= 136 bubbles per hour. The 



bubbling-period under the action 



of dilute ether became prolonged 



to 131 seconds in the course of 



8-5 minutes, the activity being 



reduced to 27. The results of 



the effect of increasing duration of 



application are given in Table X. 



The curve (fig. 15) shows 



the rate of diminution of activity 



under the action of ether. It exhibits a rapid decline 



at the beginning, which tends to reach a maximum. 



On the removal of the dilute ether and substitution 

 of normal C0 2 -solution the rate of photosynthesis was found 

 to undergo recovery. Whereas the depression of activity 



Fig. 14. The Special Plant- 

 vessel for introduction of 

 chemical substances with- 

 out mechanical disturbance 



