Plant oxydases and the chemical interrelationships of colour-varieties. 459 



species. In fact, no more suitable character could be selected for 

 demonstration of the statement that specific differences are merely 

 the outward expression of differences in chemical constitution. 



As to distribution of pigment among floweiing plants, it is ex- 

 ceptional rather than otherwise, to find a species, still more a genus, 

 from which anthoc3'anin is entirely absent. The frequent appearance 

 of colouring matter in flowers and fruit is a matter of common 

 observation; at the same time, many species develop only a trace of 

 pigment in restricted areas, such as at the nodes, in petiole bases, 

 stipules, bracts and so forth. In fact the amount of pigment produced 

 varies within Avide limits, ranging from a local development to a 

 universal colouring such as we find in the Copper Beech and many 

 Amarantaceae. 



Pigmentation and Enzyme Action. 



Until quite recently the idea of pigment formation as the out- 

 come of ferment action has been limited to those cases where the 

 result is readily apparent. As such may be quoted the rapid formation 

 of black Japanese lacquer from the white latex of the lacquer-tree 

 {Pihiis vernkifera) on exposure to air; also the discolouration of cut 

 surfaces of pears, apples, potatoes and of the fructifications of many 

 of the higher Fungi. As early as 1883, a Japanese chemist, Yoshida, 

 came to the conclusion that lacquer arose from the oxidation of the 

 latex by the aid of a peculiar enzyme in the presence of air and 

 moisture. Later researches by Bertrand^) have supported this con- 

 clusion. To the lacquer-producing ferment, which he included among 

 the oxidising enzymes (oxydases), Bertrand gave the name laccase: 

 the chromogeu, upon which the ferment acts, and which he found to 

 be an aromatic compound, he termed laccol. Subsequently he discovered 

 the enzymes laccase and tjTOsinase to be responsible for the darkening 

 of the juice of potatoes and of various fruits. Fungi, etc. In brief, 

 Bertrand was one of the first investigators to corroborate, on the 

 basis of reliable experiments, the view that various oxidising ferments 

 may act as oxygen carriers, transferring oxygen from the air to 

 colourless oxidisable substances of an aromatic nature within the 

 plant; that, moreover, the oxidised product is a pigment which by a 

 process of reduction may again be transformed into its colourless 

 chromogen. 



1) Compt. Rend. 1894, 1895, 1896. 



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