X. THE CHEMICAL CONSTITUENTS OF PLANTS 217 



True chlorophyll, as it exists in the leaves, is amorphous and is 

 phytyl chlorophyllide, i.e. : 



COOH.C 31 H 29 N 4 Mg(COOCH 3 ).COO.C 20 H 39 



but when kept in alcoholic solution it is converted by an enzyme, 

 chlorophyllase, present in almost all plants, into crystalline chlorophyll, 

 which is ethyl chlorophyllide, thus : 



C 31 H, 9 N 4 Mg(COOH)(COOCH 3 ).(COOa o H 3C j + C 2 H,OH = C 20 H W OH 



Phytol. 



+ COOH.C 31 H, 9 N 4 Mg(COOCH 3 ) COOC 2 H 5 



Ethyl chlorophyllide. 



Willstatter thinks that ordinary chlorophyll contains two compon- 

 ents, one of which, by removal of magnesia, yields phyto-chlorin, 

 C 34 H 34 O 5 N 4 , and the other phyto-rhodin, C 34 H 34 O 7 N 4 . 



Many other interesting derivatives of chlorophyll have recently 

 been obtained by Willstatter and his collaborators. 



The view that chlorophyll and haematin, the colouring matter of 

 blood, are both probably derivatives of pyrrole 



CH CH 



II II 

 CH CH 



NH 



enunciated by ScJiunck and Marchlewski in 1896 1 seems to receive 

 strong confirmation from recent investigations.- 



Moreover, Kiister finds that haematin has the composition 

 C 34 H 34 O fj N 4 Fe, which corresponds to some of the chlorophyll deriva- 

 tives, iron replacing magnesium. 



It would seem, therefore, that the red colouring matter of the 

 blood of animals, haematin, finds an exact analogue in the green 

 coloured substance so characteristic of plants, the only difference 

 being in the metal with which the organic radicle is combined. 



Possibly in plants, there is the same necessity for the presence of 

 iron, in the earlier stages of the foimation of chlorophyll and only 

 at the end of the synthetic process, is its replacement by magnesium 

 effected. 



That the replacement of iron by magnesium in this complex 

 organic molecule should produce such a complete change in the pro- 

 perties and functions of the compound is remarkable. In chlorophyll, 

 where magnesium is present, the characteristic function of the 

 compound is the decomposition of carbon dioxide in the presence of 

 water and with the energy derived from light, with the probable for- 

 mation of hydrogen peroxide and formaldehyde and the immediate de- 

 composition of the former into water and oxygen (this is probably 

 effected by enzymes associated with the protoplasm of the leaves) and 

 the polymerisation of the latter into sugar. 



1 Jour. Chem. Soc., 1896, Abstracts, i. 574. 



a Malarski and Marchlewski, Jour. Chem. Soc., 1910, Abstracts, i. 692, also 

 Willstatter and Asahina, Jour. Chem. Soc., 1912, Abstracts, i. 41. 



