16 H. A. SPOEHR 



substance a sugar-like syrup (analogous to formose) is formed 

 under conditions such as exist in the plant leaf, that this sub- 

 stance can serve as the only source of carbon for the development 

 of the plant, and finally, that plants thrive in an atmosphere of 

 formic acid in the light. These are the same criteria that have 

 been applied to the formaldehyde theory with perhaps even a 

 little less success. Yet, it seems to the writer, that this does not 

 justify the advancing of a ''formic acid hypothesis," for there 

 still is a great deal of evidence which indicates that photosynthesis 

 in the chlorophyllous leaf is a process of great complexity, the 

 chemistry of which is fully as involved as that of fermentation 

 and enzymatic action. 



