PREFACE. 



IN these pages we attempt to give a brief account of our present 

 knowledge of carbon assimilation. For this purpose we deal 

 mainly with work done durinjj the last twenty years, and we do not 

 aim at any complete historical account of the development of the 

 various aspects of the subject. Rather, as far as possible we 

 select representative pieces of work and attempt to arrange the 

 facts brought out in these investigations so as to give a clear 

 conception of the present position of the various problems. 



It may be that this review will appear to the reader to be very 

 critical. In this case we hope it will not be concluded that the 

 writers fail to appreciate the efforts of the many contributors to 

 the subject, both along its main lines and its side channels. Our 

 desire is to emphasize those facts which will help towards the 

 realisation of the idea that the work done on carbon assimilation 

 justifies the position of plant physiology among the pure sciences. 

 It is to be hoped that this realisation will stimulate plant physiolo- 

 gists to attempt a similar development of our knowledge of other 

 phases of the life of the plant. 



A I'ecent botanical writer has said that the function of pure 

 science is to pursue useful knowledge; the duty of the leaders of 

 science to direct the pursuit along what appear to them the most 

 promising lines. 



This proposition we regard as thoroughly unsound. It is 

 impossible, for instance, in plant physiology for anyone to foretell 

 which particular plant process is the most promising one to 

 investigate in order to obtain results of utilitarian value. It is true 

 indeed that the economic importance of a pure science depends 

 upon the utilisation of the principles evolved by it. Thus the ever- 

 growing importance of plant physiology is due to the fact that the 

 principles brought out by it are utilised in plant cultivation. But 

 the growth and development of a pure science cannot be controlled 

 by the applied science dependent upon it. 



Although the principles of carbon assimilation exposed in this 



review may still appear somewhat vague, yet they have sufficient 



definiteness to indicate that their application in agriculture will 



open up new possibilities of development in that field. For this 



reason we hope that the following pages will be of interest to those 



concerned in the development of scientific agriculture, as well as to 



those interested in plant physiology for its own sake. 



I.J. 



London, W.S 



April, 1917, 



