MEMOIRS. 



Pringsheim's Researches on Chlorophyll.^ Translated 

 and condensed by Professor Bayley Balfour, of Glasgow 

 University. (With Plates VIII and IX.) 



{Continued.) 



V. Assimilation and Colour. 



The known facts regarding assimilation in plants are not 

 in opposition to the view here advocated, that the colour 

 only indirectly, tlirough respiration, takes part in this 

 process, and that the colouring matter has no share in 

 decomposing carbonic acid. 



A. Chemical Hypotheses of Chlorophyll Function,^ — Out of 

 the general notion that chlorophyll colouring matter plays 

 a direct part in assimilation, has developed the idea that its 

 substance enters directly into the process of decomposition 

 of carbonic acid, and that in this process it is constantly 

 being destroyed and regenerated. This must be the basis 

 of any chemical hypothesis of its function in assimilation. 

 It not only assumes the destruction in light (and in daylight 

 of medium brightness) of colouring matter, but also that 

 this destruction is a consequence of appropriation of the 

 carbon drawn from the carbonic acid decomposed. The 

 carbon-compounds formed through assimilation in the plant 

 body, would 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-compounds to the chlorophyll 



' • XJntersuchungen iiber Lichtwirkung und Chlorophyll function in der 

 Pflanze.' Von N. Pringsheim, S. 152, mit 16 lithographirten Tafeln. 

 Leipzig, 1881. 



* See Sachsse : ' Die Chemie und Physiologie der Farbstoffe, Kohlen- 

 hydrate,' &c., Leipzig, 1877 ; and Wiesner, ' Die Enstehung des Chloro- 

 phylls,' Wien, 1877, for details regarding chemical hypotheses. 



VOL. XSII. NEW SER. H 



