200 Alfred J. Etvdvt : 



tion. Against this possibility we have the fact that free oxygen 

 oxidizes carotin more rapidly than xanthophyll, and that the only 

 reductases which seem able to effect the reduction of xanthophyll to 

 carotin appear to be such as themselves readily combine with free 

 oxygen. 



In the absence of light the presence of a film of carotin or xan- 

 thophyll on the surface of the chloroplastid would render the further 

 penetration of carbon dioxide very slow, and would largely protect 

 the chlorophyll, so long as the plastid was living, from decomposition 

 by carbon dioxide during darkness. 



Tlie now well recognised fact that chloroplastids may be rendered 

 temporarily inactive without necessarily being killed, and while 

 appearing normal, l is sufficient evidence that the continued assimi- 

 lation of carbon-dioxide involves a definite relationship between 

 the chlorophyll and protoplasm of the chloroplastid. In other 

 words the physical structure of the chloroplastid may be as impor- 

 tant as the chemical composition of chlorophyll. Some special 

 arrangement must exist to protect the chlorophyll from the direct 

 chemical action of the carbon dioxide, which would otherwise re- 

 move the magnesium from the clilorophyll and convert it into 

 phaeophytin. 



7''he poli/merizatioj} of fornudchhyde. 



Butlerow (Liebeg's Annalen, 120, p. 295, 1861) obtained a bitter 

 tasting syrup " methylenitan," by the action of lime water on 

 trioxymethylene, a polymer of formaldehyde. Loew obtained a 

 sweet syrup by the prolonged action of lime water on "4% formal- 

 dehyde. Euler has shown that when a 2% solution of formaldehyde 

 is heated for some hours with calcium carbonate, arabinoketose, a 

 pentose sugar, is jjroduced with glycollicaldehyde as an inter- 

 mediate product. According to Czapek (Biochemie, 1913, Vol. 1, 

 p. 628), glucose is not produced by the action of alkalies on for- 

 maldehyde, but only non-fermentable sugars such as i-Fructose^ and 

 i-arabinoketose. Fischer, however, obtained from Loew's crude 

 formose an " acrose " sugar, which he was able to convert into 

 levulose. 



Both Loew's and Euler's methods are slow and tedious to carry 

 out. A rapid method is as follows : — A saturated solution of for- 

 maldehyde is mixed with six times its volume of lime water, and 



1 Ewart, Journal Linnean Soo=pty, 1896, vol. xxxi., p. 364. 



2 Ordinary fructose is fermentable by yeast. See Harden and Yonn<;-, Proc. Roy. Soc. 

 London, B., 1910. 82, p. 645. 



