Daniel 1. Anion 



335 



The hypothesis was tested in the following manner. Isolated chloro- 

 plast fragments were illuminated, without, however, adding the oxi- 

 dant (in this case ferricyanide) which is necessary for the evolution of 

 oxygen to take place. In one instance, chloride was added to the illumi- 

 nated chloroplasts; the control contained no chloride. After twenty 

 minutes of pre-exposure to light, the oxidant was added and the photo- 

 chemical oxygen evolution was measured manometrically. To the 



ro 



E 

 E 



O 



"O 

 O 



c\j 



20 30 



Minutes 



Figure 3. Protective effect of chloride on illuminated sugar beet chloro- 

 plast fragments. Circles: Illuminated for 20 min. in the presence of chloride. 

 At t = 20 min. tipped in the oxidant (ferricyanide) to the manometer 

 vessel. Crosses: illuminated for 20 min. in the absence of chloride. At t = 

 20 min. chloride and ferricyanide were added simultaneously. The con- 

 centration of chloride was 0.01M KC1. 1.5 X io -7 moles of K.Fe(CN) 6 

 was added to each vessel. Conditions not specified were the same as those 

 given in the legend for Figure 1. 



