PREFACE Vll 



and made available. From the quantitative relation 

 between the volume of the carbon dioxide absorbed and 

 that of the oxygen evolved, it was concluded that the first 

 organic product formed in the plant is a carbohydrate : a 

 conclusion confirmed by the observation that, in most 

 plants, the carbohydrate formed is stored in the chloro- 

 plasts as starch-grains. Further knowledge has been 

 accumulated as to the relation of the assimilatory process 

 to temperature ; as to the relative efficiency of light of 

 different colours and degrees of intensity ; and as to the 

 most suitable proportion of carbon dioxide to be supplied 

 by the medium surrounding the plant. 



It would appear, therefore, that almost everything that 

 can be known about photosynthesis has now been ascer- 

 tained. It may be admitted that this is approximately 

 true in the qualitative sense, but certainly not in the 

 quantitative sense. In spite of many laborious researches, 

 it is not yet possible to attach definite numerical values 

 to the efficiency of light of various wave-length and energy ; 

 nor to the effect of a rise of temperature, or of a variation in 

 the amount of available carbon dioxide, upon the activity 

 of photosynthesis. 



The present volume is essentially a record of quantitative 

 research in these various directions. The experiments have 

 been carried out by means of a variety of sensitive apparatus 

 specially devised for the different objects in view ; and the 

 results, having been recorded automatically, are at least 

 free from the error of the personal equation. 



The author takes this opportunity of expressing his 

 high appreciation of the valuable assistance given to him, 

 in carrying out the numerous and often prolonged experi- 

 ments, by Professor N. C. Nag, M.A., the Assistant Director, 

 and by the Scholars of the Bose Institute. 



Bose Institute, Calcutta, 

 October, 1923. 



J. C. Bose. 



