206 Alfred J. Eivart : 



The removal of the magnesium from clilorophyll by carbon 

 dioxide, and the fact that magnesium will l>ring about the combina- 

 tion of carbon dioxide and water to formaldehyde suggests at first 

 sight a possible explanation of carbon dioxide assimilation. This 

 action, however, takes place as well in darkness as in light. Fur- 

 ther, the magnesium is separated from chlorophyll as the carbonate, 

 and not in the form of the metal, and if any such action was 

 necessary in photo-synthesis, when the latter was active, tlie bulk 

 of the chlorophyll would exist in the form of phaeophytin, and the 

 leaf should lose its green colour, which is not the case. Carbon 

 ■dioxide decompose the chlorophyll in heaped grass leaves in dark- 

 ness, but in living leaves exposed to light in air rich with CO-o, the 

 chlorophyll remains green. If no carbon dioxide is present, and 

 the illumination is strong, the chlorophyll slowly bleaches, but this 

 is stopped if the supply of carbon dioxide is proportionately in- 

 creased. 



It is more reasonable, therefore, to suppose that the chlorophyll 

 as a whole takes part in photo-synthesis, acting as a light fer- 

 ment, or lytase enzyme, which, using light energy to draw carbon 

 dioxide and water into its own organisation, breaks down again, 

 liberating them as carbohydrates, and that so long as the supply 

 ■of CO-o corresponds to the intensity of the light, and the joroducts 

 are removed, the decomposition and reconstruction of the chloro- 

 phyll remain in equilibrium. 



There is no difficulty about the decomposition of chlorophyll, but 

 evidence of its regeneration is difficult to obtain. 



In a previous paperi an account was given of various attempts 

 made to bring about the regeneration of chlorophyll outside the 

 plant. Although indications were obtained suggesting that this 

 might be possible, these were not conclusive. Further attempts in 

 the same direction have so far completely failed. It was frequently 

 observed that in the separation of chlorophyll, alcoholic solutions 

 of xanthophyll, containing the waxy derivatives by precursors of 

 chlorophyll in finely suspended form, when evaporated formed 

 greenish yellow skins, which contained chlorophyll, and left the 

 remaining liquid with little xanthophyll. This happened even when 

 the watery alcoholic liquid showed no trace of chlorophyll under 

 the spectroscope. Further investigations showed, however, that 

 when alcoholic solutions of pure xanthophyll containing a little 

 water are evaporated slowly, the first pnrt of the xanthophyll to 



1 Pioc. Hoy. Sor. [,01x1., B., vol. 80, p. 30, 1908. 



