g6 Carbon Assimilation. 



Chapter V. 



The Products of Carbon Assimilation. 



A. General Remarks. 



In this chapter we propose to deal with the production of 

 substances in the leaf as a result of the assimilatory processes. 

 We shall confine our attention here to a consideration of the 

 substances known to be produced ; later we shall deal with the 

 theories of carbon assimilation advanced to explain the production 

 of these substances. 



The substances which are known to be produced as a result 

 of carbon assimilation are oxygen and carbohydrates, and the 

 evolution of oxygen by the green plant in sunlight was one of the 

 earliest known facts of plant physiology. 



Although a few workers have made investigations on the laws 

 governing the evolution of oxygen in sunlight, notably de Saussure 

 (1804), Bonnier and Mangin (J886) and Maquenne and Demoussy 

 (1913), yet ^e subject is one which has probably received less 

 attention than any other aspect of carbon assimilation, and of 

 recent years seems scarcely to have attracted that attention which 

 it deserves. 



The fo rmation of carbohydrates in_the leaf as a result of 

 assimilation was not recognised until the classical researches of 

 Sacj3S-(1862) established this fundamental fact. Since then the 

 production of carbohydrates in the leaf has been the subject of 

 almost continual research, notably by English workers, yet it 

 cannot be claimed that even now our knowledge of the organic 

 products of carbon assimilation is very definite. 



Although the production of oxygen and of carbohydfates in the 

 leaf are merely two different aspects of the same process or set of 

 processes, yet the two have always been investigated quite 

 independently of one another. It is therefore convenient to discuss 

 these two questions separately, and we shall therefore in the 

 following section of this chapter review our present knowledge 

 regarding the evolution of oxygen from the assimilating leaf, before 

 passing on to consider the various questions raised in connection 

 with the formation of organic material. 



B. The Evolution of Oxygen. 



That green parts of plants under the influence of light evolve 

 oxygen, was established by Priestley, Senebier and Ingenhouss 

 towards the end of the eighteenth century, but it was de Saussure 



