186 Ingvar Jorgensen and Walter Stiles. 
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 (1886) and Maquenne and Demoussy 
(1913), yet the 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 formation of carbohydrates in the leaf as a result of 
assimilation was not recognised until the classical researches of 
Sachs (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 carbohydrates 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 
