120 pringsheim's researches on chlorophyll. 



and in green organs this inhalation of oxygen increases 

 considerably in light. Respiration, then, in green organs 

 exposed to light in a limited atmosphere necessitates a 

 diminution in the gas-volume thereof. 



If, now, the gas-volume around an assimilating and 

 respiring plant remains constant, the immediate product of 

 the reducing process must be a substance poorer in oxygen 

 than a carbo-hydrate, and poorer by that amount of oxygen 

 used up i» the respiratory process. This conclusion is 

 inevitable if the carbon-compounds are directly formed from 

 the carbonic acid and water. 



But, it might be supposed that the constancy of gas- 

 volume observed under certain conditions only occurs if 

 there is a definite amount of respiration, only if the primary 

 reduction-product combining with oxygen is transformed 

 almost entirely to a carbo-hydrate, which then persists as 

 a stable reserve-substance in the chlorophyll -corpuscles resist- 

 ing further oxidation in light. The amount of respiration 

 in a green tissue would in that case influence not only the 

 observed gas-interchange, but also determine the character 

 of the formed compounds deposited within the chlorophyll- 

 corpuscles. The function of these corpuscles is a double one, 

 they assimilate and they respire ; and one is naturally led, on 

 this account, to the hypothesis dealt with in the next chapter, 

 that it is the accumulation of colouring matter which 

 brings about the formation of different construction-products 

 in the chlorophyll-corpuscles, that is to say, through respi- 

 ration in the chlorophyll- corpuscle a primarily rich-in- 

 carbon but poor-in-oxygen direct product of the reducing 

 process passes into a more highly oxidised compound, 

 the extent of oxidation being influenced by the amount of 

 respiration in the corpuscle consequent upon the varying 

 brightness of light reaching it, which in turn depends on 

 the depth of colour in the tissues. 



Chlorophyll colouring matter is thus by its absorption of 

 so-called chemical rays, the constant regulator of respiration 

 and assimilation, whilst its absorption in the red may 

 perhaps increase the heat eflPect of these rays on the plant. 



VI. The Formation of Hypochlorin in Young Seedling Plants y 

 and its Relation to Assimilation. 



From the point of view of the double function of. chloro- 

 phyll-corpuscles enunciated in the last chapter, the formative 

 substances found in them must be the result of the combined 

 action of assimilation and respiration. Of the enclosed 



