pringsheim's researches on chlorophyll. l21 



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 con- 

 sider the origin and construction of all bodies enclosed in 

 the chloi'ophyll-coi'puscles, a word with regard to the con- 

 nection 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 dependence upon light and 

 carbonic acid siipported 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 chloro- 

 phyll-corpuscles, and also of tannin as it occurs in Mesocar- 

 pus, and indeed of all the ternary, rich-in-carbon, compounds 

 hitherto known in the plant-body. The 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 

 substance which is a constant and essential product of 

 assimilation in the corpuscles is hypochlorin. The idea that 

 the primary product of assimilation may vary in different 

 plants, and that these substances may thus all be direct pro- 

 ducts under different conditions, is improbable and of 

 no explanatory value. No fact positively forbids such a 

 notion, but the similarity in structure and composition of 

 the chlorophyll-corpuscles, and the great agreement in gas- 

 interchange amongst green tissues, indicates an identity, 

 in all, of the assimilation-process. Whatever theory be 

 adopted there remains to be explained how it is that in 

 one plant starch or fat or it may be both these substances, 

 in another tannin or perhaps sugar, and in all hypochlorin, 

 are formed and deposited inside the chlorophyll-corpuscles. 



The theory here advanced is based upon the absorption of 

 oxygen by the chlorophyll-corpuscles and upon the chemical 



' 'Bot. Zeit..,' 18G2, p. 3G5 ; ' Elora,' 1SG3, p. 165, 1863, "p. 193; 

 Jahrb. f. Wiss. liot.,' iii (18G3) p. l'J9 ; ' Bot. Zeit.,' ISCi, p. 2S9 ; 

 Experimental Physiologic,' p. 133. 



