10 



PREFACE 



pearecl that they have obtained a perfect impression and they have en- 

 deavored to construct a complete picture on the basis of their knowledge. 

 Very few of these pictures, which have taken the form of theories of the 

 mechanism of photosynthesis, have stood the test of time. They have 

 served by pointing out the need of accumulating more precise knowledge 

 and by emphasizing the necessity of applying a wider range of vision in 

 formulating conceptions of the working of organic nature. 



Because of the fact that the phenomenon of photosynthesis has been 

 considered from many different sides, publications on the subject are 

 scattered through many different scientific journals. The literature of 

 the subject is also very extensive. It has not been the object to achieve 

 the inclusion of full references on all of the subjects discussed. Nor are 

 all papers which have been published given discussion ; this would result 

 in great prolixity. An endeavor has been made to discuss the salient 

 features of the subject with some consideration of those theoretical as- 

 pects which offer promise of fruitful development on the basis of experi- 

 mental study. 



H. A. S. 



Carmel-by-the-Sea 

 California 

 April, 1926 



