338 President's Address. 



therefore be derived from the chlorophyll colouring matter as a 

 mother-substance. This is, however, entirely hypothetical, and has 

 no support from the side of organic chemistry, nor from direct 

 experiment. The assumed genetic relations of the carbon com- 

 pounds to the chlorophyll colouring matter are not explained, and, 

 indeed, the constitution 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 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, it is easily altered and con- 

 verted into resin. This is the weak point in all chemical considera- 

 tions 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 chlorophyll is entirely 

 hypothetical. The 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 chloro- 

 phyll colouring matter in light in direct connection with the de- 

 composition 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 signifi- 

 cance, but the facts adduced contradict decisively every theory based 

 on the destruction of chlorophyll in the reducing process, show- 

 ing— 



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 assimila- 

 tion is possible. 



3. The destruction of chlorophyll colouring matter is a patho- 

 logical process, and the colouring matter once destroyed is never 

 regenerated. 



But it may be asked, Is the colouring matter a necessary con- 



