114 PRINGSHEIM S RESEARCHES ON CHLOROPHYLL. 



colouring matter are not explained, and, indeed, the consti- 

 tution of the colouring matter — notwithstanding recent work 

 on the so-called chlorophyll-crystals — is still as good as 

 unknown. For the red and green crystals which can be 

 extracted from artificial chlorophyll- solutions are by external 

 characters, and by their spectra, proved to be in no way 

 identical with the deeply-coloured green drops which exude 

 from the chlorophyll-corpuscles, as described in this paper, or 

 which, after the solvent has been removed, can be obtained 

 from a solution of chlorophyll; and in them the normal 

 colouring matter as it occurs in the tissues is obtained, still 

 attached to its vehicle, from which, indeed, in the unchanged 

 condition it has never yet been separated, and with which, after 

 separation from the tissue, itis easily altered and converted into 

 resin. This is the weak point in all chemical considerations 

 of the genetic relations between chlorophyll colouring matter 

 and the other contents of the cell, and at the present time 

 the formation of carbo-hydrates out of the clilorophyll is en- 

 tirely hypothetical. iMie destruction of chlorophyll colouring 

 matter in daylight of medium intensity in which assimilation 

 is possible, is quite unproved, improbable, and against all 

 experience, and the whole chemical hypothesis based on such 

 destruction of the chlorophyll colouring matter in light in 

 direct connection with the decomposition of carbonic acid is 

 quite untenable. 



To the purely physical theory of chlorophyll-function 

 here brought forward, the origin of the chlorophyll colouring 

 matter and its genetic relations to the other cell-elements, 

 are of incidental significance, but the facts adduced con- 

 tradict decisively every theory based on the destruction of 

 chlorophyll in the reducing process, showing — 



1. Destruction of chlorophyll colouring matter in the 

 living cell in light is an oxidation process independent of the 

 presence of carbonic acid. 



2. Chlorophyll colouring matter is not destroyed in light 

 when in an atmosphere of carbonic acid and hydrogen in 

 which assimilation is possible. 



3. The destruction of chlorophyll colouring matter is a 

 pathological process, and the colouring matter once destroyed 

 is never regenerated. 



B. Is the Colouring Matter a necessary condition for Assimi- 

 lation ? — Another theory, which regards chlorophyll colouring 

 matter as a necessary condition for the decomposition of 

 carbonic acid and water, assumes that it serves as a me- 

 dium of transfer for the light, It absorbs rays of light which 



