Precursors of CJdoro'phyll. 193 



Hence impure chlorophyll appears to spontaneously undergo 

 partial segregation into carotin and xanthophyll, and pale brown 

 waxy solids rich in magnesium. In addition small quantities of 

 formaldehyde appear. An equation for the production of glauco- 

 phyllin and carotin from chlorophyll cannot be made to balance 

 without the addition of oxygen, but small quantities of dissolved or 

 occluded oxygen might have been present before sealing, as this 

 possibility was overlooked, In that case a suggested equation 

 might be — 



(cOOC,oH3, 



If a similar change resulted in the production of the monocar- 

 boxylic phyllophyllin (CgiH.nNjMg.COOOH) still less oxygen would be 

 required. 



In samples of chlorophyll purified by precipitation, no carotin or 

 xanthophyll appeared, and dry samples kept in sealed vacuum 

 tubes were apparently unaltered after five months in darkness. In 

 the case of dry samples from the unpurified petrol ether extract, 

 after keeping for some months, the sample will flow slowly over the 

 glass, and shows a separation of solid red carotin or xanthophyll 

 particles. 



The Precursors of Chloroj)hyU. 



According to Timiriazeff'i and to Monteverde2 etiolated leaves yield 

 a small amount of fluorescent pigment which they term " proto- 

 chlorophyll," This, according to Monteverde and Lubimenko,^ is 

 a derivative of the labile " chlorophyllogen." which rapidly turns 

 into chlorophyll when exposed to light. The precursor of this 

 theoretical substance is. according to the same authors, a colourless 

 theoretical substance, " leucophyll." 



Kohl* showed that etiolated seedlings contained carotin in 

 abundance, and even doubted whether any other pigment was pre- 

 sent. He also found that the percentage of carotin did not decrease 

 during the formation of chlorophyll on exposure to light, and 

 hence denied that any conversion of carotin into chlorophyll com- 

 ponents took place. Kohl's observation might, however, merely 

 indicate that while food materials were abundant, the production 



1 Conipt,. rend.. 102, 686 (1886) ; 414 (1889). 



•2 Acta. Horti. Petropol., 13, 201 (18S4); Bull. Lard. Imp. Dot. Pecrograd, 7, 37 (1907). 



3 Biol. Central, 31, 449 (1911) ; Bull. Ac. Imp. Sci. Pctro-rad, 73 (1911) ; 609 (101-2). 



4 Untersuchungen iiber Carotin, 7.'> (1902). 



