LECTURE XI 



MODERN VIEWS ON THE COMPOSITION OF CHLOROPHYLL 



IN a previous lecture I attempted to trace very briefly 

 the progress in our knowledge of chlorophyll and its 

 functions down to the beginning of the twentieth century. 

 I must now endeavour to tell you, even more briefly, 

 the main additions made during the last two decades. 

 I told you that, although quite a small army of chemists 

 and botanists -had been struggling to determine what 

 chlorophyll really consisted of was it one pigment or 

 a mixture of several, what were its decomposition products, 

 and so on the problem was left in a condition so confused 

 that the average botanical student, unskilled in the 

 intricacies of chemical manipulation, was in a fair way 

 to .give up the whole subject as hopelessly incompre- 

 hensible. Of recent years, however, chiefly due to the 

 labours of Willstatter and his pupils, we have at last 

 apparently reached some measure of finality in this most 

 difficult line of research, and the results achieved have, 

 fortunately, been summarised for us by Willstatter himself, 

 in conjunction with his colleague, Stoll, in their volume 

 entitled Untersuchungen tiber Chlorophyll, Methoden und 

 Ergebnisse, published in 1913. This work runs to over 

 400 pages, and therefore you will not expect me in a 

 few minutes to give you more than the very briefest 

 abstract of the authors' results. 



The outstanding conclusions at which Willstatter 

 arrives from an immense number of analyses is that leaf 

 green is a complex pigment in which may be recognised 



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