= 85 = 



stable in the living plants. This result indicates that photosynthesis 

 occurs vd.thout conversion of the principal pigments into other colored 

 substances or into colorless products that are reformed under the action 

 of light and air. From this standpoint, the chloroplast pigment system i 

 is an organic antenna that collects the energy of sunlight for photo- 

 synthesis without itself \andergoing extensive chemical change or alter- 

 ationo 



The pigment system consisting of chlorophyll a^ plus or minus other 

 chlorophylls^, xanthophylls, and one or more carotenes is characteristic 

 of autotrophic plants growing under natural conditionso The only prin- 

 cipal pigment common to all the organisms examined was chlorophyll a^o 

 Yet the fact that this chlorophyll a was not found unaccompanied by 

 carotenoids suggests that the carotenoids play an indispensable role 

 in the fonnation, maintenance, structure, or function of the photo- 

 synthetic apparatus. 



At the present stage of our knowledge about the photo synthetic 

 process, it is possible to fancy a variety of mechanisms whereby the 

 energy of sunlight is transformed to chemical potential energy by the 

 production of organic matter and oxygen through the intermediary ac= 

 tion of the pigments. But the precise mechanism has yet to be eluci- 

 dated o 



