344 President's Address. 



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

 passes into a more bigbly oxidised compound, the extent of oxida- 

 tion being influenced by the amount of respiration in the corpuscle 

 conseijuent upon the varying brightness of light reaching it, which 

 in turn depends on the depth of colour in the tissues. 



Chlorophyll colouring matter by its absorption of so-called 

 chemical rays is the constant regulator of respiration and assimila- 

 tion, whilst its absorption in the red may perhaps increase the heat 

 effect of these rays on the plant. 



Under the heading, 



The Formation of HypoMorin in Young Seedling Plants, and its 

 Relation to Assimilation. 



Pringsheim states shortly the conclusions to which his in- 

 vestigation lead him as to the true function of chorophyll. 



From the point of view of the double function of chlorophyll- 

 corpuscles already enunciated, the formative substances found in 

 them must be the result of the combined action of assimilation 

 and respiration. Of the enclosed bodies which are to be used up 

 in metastasis, the chief are starch, fat, perhaps sugar, tannin, 

 and hypochlorin. All of them, it is here maintained, cannot be 

 immediate products of the reducing process ; probably hypochlorin 

 is the primary assimilation product. As every assimilation theory 

 must consider the origin and construction of all bodies enclosed in 

 the chlorophyll-corpuscles, a word with regard to the connection of 

 all these substances with chlorophyll function may be said. 



Controversy about the physiological value of these bodies has 

 hitherto been confined to the question of the primary assimilation 

 product. Starch, having been for long the only highly carbonised 

 content of chlorophyll-corpuscles known, was considered as such, 

 and its wide distribution, and, as Sachs has clearly shown, its de- 

 pendence upon light and carbonic acid, supported this view. But 

 starch, as is now known, is not the only, nor yet universal, but 

 merely one of the most abundant products of assimilation. The 

 like may be said of fat and sugar, each of which has been regarded 

 as the first outcome of the reducing process, although the latter has 

 never been proved to exist in chlorophyll-corpuscles, and also of 

 tannin as it occurs in Mesocarpus, and indeed of all the ternary, 

 rich-in-carbonj compounds hitherto known in the plant body. Tlie 

 origin of each and all of these, not one of which is universally 

 present in chlorophyll-corpuscles, is doubtless to be ultimately 

 traced to the reduction in light of carbonic acid, but the only sub- 



