INTRODUCTION 



S o eager are we for energy that anything we think capable of 

 supplying it will capture our interest. The atom has just made 

 a triumphant entry into our schedule of resources because 

 we see the possibiUty of using the energy that hes hidden 

 within it. 



The general infatuation for these new sources must not 

 make us forget or underestimate our most solid capital, on 

 which we have lived up to the present, which feeds us, clothes 

 us and warms us — the energy stored and put at our disposal 

 by chlorophyll. 



Is it possible to overestimate the importance of chlorophyll? 

 We can do without atomic energy and until today humanity 

 lived without having discovered it, but, without chlorophyll, 

 no man and no animal could survive a day on earth. MilHons 

 of centuries before the first man saw the hght, the humble and 

 discreet chlorophyll in the remote past prepared for his 

 coming. 



In making known the work of this most indispensable 

 servant of life, we shall recall first how its role and its 

 importance were discovered and show that we have recently 

 been able to form an idea, although still very imperfect, of 

 the nature of its activity. 



We shall introduce, then, chlorophyll, that substance — or 

 rather those chemical substances — located in the chloroplasts 

 of green leaves, study its general properties and see how it 

 appears, works and disappears. 



Although we do not know exactly what happenes inside the 

 leaf, the progress of biochemistry, of which this is perhaps the 

 greatest achievement in the last ten years, has enabled us to 

 acquire some understanding of the chemical processes of 

 photosynthesis or assimilation. Later we shall examine the 



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