2 STUDIES IN PLANT EESPIRATION AND PHOTOSYNTHESIS. 



It would seem, then, that the true province of plant chemistry 

 should be the unraveling of the tangle of chemical reactions which 

 give rise to this mass of carbon compounds and ultimately to deter- 

 mine the function of these reactions in the economy of the living 

 plant. Historically, what is now termed organic chemistry had its 

 origin in such a task. But the chemist discovered that he could find 

 a large number of short cuts; that the intermediary action of living 

 things was not essential to the production of most of the substances 

 found in nature; that, in fact, he could greatly improve on nature in 

 the production of the multifarious substances of use in industry 

 and the arts. 



In some respects the present has its points of similarity with the 

 time of Woehler and Liebig. Much sober thought is now being 

 given to the fundamental difference between the living and the 

 non-living. The first flush of success of the purely mechanistic 

 interpretation of life processes has paled as the enormous difficulties 

 of applying this conception to the highly intricate and manifold 

 manifestations of life have been more clearly recognized. The 

 methods and modes of transforming matter followed by the chemist 

 and by the living organism are perhaps not as similar as appears at 

 first glance. At first we were primarily interested in the final goal, 

 the products of material transformations; but, in chemistry as well 

 as in physiology, as we follow more closely the energetics of such 

 transformation, many almost irreconcilable differences arise which, 

 before the two can be brought together, necessitate sweeping com- 

 promises to the unknown and indefinite. And it is this question of 

 energy which is forcing us to a deeper study of living things. The 

 scientific world is awakening to the necessity of taking stock of our 

 available sources of energy. Repeatedly attention has been called 

 to the inexhaustible floods of solar energy and to the extensive use 

 of plant products to drive the machinery of our civilization. Car- 

 bohydrates are to prevent the too-rapid exhaustion of our oil and 

 coal resources. As the realization of the limits of our energy re- 

 sources has become more general, reliance on the magic accomplish- 

 ments of the chemist has increased, and the chemists, with cool 

 theoretical nonchalance, have pointed to the untold possibilities of 

 solar energy. But the living chlorophyllous plant still remains the 

 only converter of solar energy! 



The chemical reaction most fundamental to all living things, 

 the photosynthetic process, the bridge between the inanimate and 

 the animate, the source of most of our energy, has stubbornly resisted 

 all attempts at solution by physico-chemical methods. Here it has 

 become plainly evident that while physiology is rife with chemical 

 possibilities, physiological experience alone is the guide to the inter- 

 pretation of biological processes. Furthermore, it has become clear 



