92 CHAP. XII. EFFECT OF INTERMITTENT LIGHT 



intermission. The presence of this turning-point would, 

 moreover, prove to be a crucial test for the important 

 factor of photo-molecular strain : for the retardation in- 

 duced by the absorption-respiration factor would increase 

 continuously without any turning-point. 



There is a further modification due to rapid intermission 

 which will be presently explained. 



Effect of Intermittent Sky Light 



The following is an account of experiments carried out 

 on the above lines. The plant-vessel was enclosed in a 



Fig. 27. The Effect of Intermittent Light on Photosynthetic 



Activity- 

 First line c is the record under continuous light. The record in the 

 second line is of intermission of 0-5 second, the last dot 

 being slightly to the left, indicating slightly enhanced 

 efficiency. In the third and succeeding lines note the increase 

 in the bubbling-period as seen in the shifting of the last dot 

 to the right (sky light). 



dark box, provided with a photographic shutter worked 

 by a special clockwork by which intermittent exposure 

 consisting of equal alternating periods of light and darkness 

 was produced, the periods being o • 5, 1, 2, 3, 5 and 10 seconds. 



