Summary. . 209 



With an excess of carbon dioxide and a deficiency of light, stage 

 1 would preponderate. With stronger illumination .stages 2 and 

 3 would balance 1. With excessive illumination and a deficiency 

 of carbon dioxide disintegratory photo-oxidation would take place, 

 and the amount of chlorophyll would he reduced. 



In the assimilation of carbon dioxide chlorophyll acts as a light 

 energizing enzyme, and takes direct part in the cycle of chemical 

 changes, which probably have carotin, xanthophyll, phytyl and 

 glaucophyllins as intermediate products and glucose, levulose, for- 

 maldehyde and oxygen as end products. The sugar may be formed 

 directly as well as through the polymerization of formaldehyde. 



A large part of the energy represented by the carbohydrate 

 products is absorbed during the reconstruction of the chlorophyll 

 molecule. 



Carbon dioxide decomposes extracted chlorophyll both in light and 

 The earlier supposition that zanthophyll was one of the products 

 has not been sustained. In the presence of zinc dust, the zinc takes 

 the place of the magnesium, and the chlorophyll i-emains green as a 

 in darknncc.. removing its magnesium, and producing phaeophytin. 

 stable zinc chlorophyll. 



Apart from its protective function, carotin seems to be especially 

 important as providing during its photo-oxidation or partial dis- 

 integration, the massive hydrocarbon combination in the phytyl 

 radicle of chlorophyll wliose addition is necessary to convert the 

 dicarboxylic glaucophyllin into the tricarboxylic chlorophyll. 

 Xanthophyll can be reduced to carotin by the aid of metallic re- 

 ductases, but no oxidases have been found capable of converting 

 carotin into xanthopliyll. The oxidation of these substances in 

 darkness or in feeble light differs in certain re.spects from that 

 taking: place in intense light. 



The oxidation of rhodophyllin, chlorophyll, xanthophyll, and 

 carotin is more rapid at high temperatures than at low ones, and 

 the rates of oxidation are in the order given, carotin being most 

 readily oxidized. 



A rapid method is described of polmerizing formaldehyde to 

 sugar, which has a definite end reaction, and yields* calcium 

 and sodium tartrates as bye-products. 



