196 Alfred J. Ewart : 



of the progressive decomi>osition of clilorophyll in darkness. In 

 any case the formation of a pigment of this character is darkened 

 leaves in unusual. Extractions of additional material, with alco- 

 holic potash containing a little water yielded potassium rhodophyl- 

 lin, but Avhether this was partly responsible for the red colour or 

 was merely derived from the chlorophyll, is impossible to say. 



In the case of most green leaves, the chlorophyll decomposes more 

 or less rapidly in darkness. This is possibly primarily due to the- 

 action of the carbon dioxide produced by respiration, aided by sub- 

 sequent oxidation, and l)y the absence of the chlorophyll regenera- 

 tion normally carried on in the presence of light. It is worthy of 

 note that in fleshy plants such as cacti, Avhere in darkness a forma- 

 tion of organic acids may largely replace the normal carbon dioxide 

 production, the leaves remain green unusually long in darkness. 

 The same applies to water plants such as Elodea and Chara, in 

 which the carbon dioxide is removed in solution by the water out- 

 side. 



The yhot o-o.ridation of rhodoplxyllin. 



An alcoholic solution of chlorophyll containing a little water was 

 heated on a water bath with potash for twelve hours. Excess of 

 water was added, and the liquid was placed in a stoppered Win- 

 chester, shaken and allowed to settle daily for three days. The 

 supernatant liquid was syphoned off, and the residue filtered. The 

 residue was Avell washed with water, dried washed with a little 

 absolute alcohol, and then treated with hot alcohol containing a 

 little water. The red filtrate on standing formed red crystalline 

 platelets, with a bluish metallic lustre. From this potassium- 

 rhodophyllin, rhodophyllin was obtained by treating with acid 

 sodium johosphate and subsequent separation.! The product was 

 readily soluble in ether ajid alcohol. 



l^'ilms and watery emulsions of rhodophyllin and of its potassium- 

 salt were exposed to light. The latter was slightly more resistant 

 to photo-oxidation than the former, l>ut both proved to be much 

 more stable and resistant to i^hoto. -oxidation than either chloro- 

 phyll or xanthophyll. No formaldehyde or reducing sugar could 

 be detected as a product of the photo-oxidation, either in the 

 absence or in the pre.sence of carbon dioxide. 



Since rhodophyllin is comparatively stable, and resistant to 

 photo-oxidation, it Avould be natural to find that it would be one 

 of the products of the decomposition of chlorophyll in autumnal 



1 WiHstaUer ai-.d Pfannestiil, Aniialen, 358, 1908, v- 205. 



