Plant oxydases and the chemical iuterrelationsûips of colour-varieties. 473 



Note added May 6th 1910. 



Since writiDg the above account I have come to the conclusion 

 that the rapid formation of a brown or reddish-brown colouration in 

 many genera under the influence of chloroform vapour is due to the 

 action of a glucoside- splitting ferment in connection with an 0x3^- 

 dase. It is an established fact that exposure to the action of an- 

 esthetics brings about the interaction between glucosides and their 

 corresponding ferments.^) Thus, for instance, plants containing cyano- 

 genetic and mustard-oil glucosides produce the characteristic odours 

 of prussic acid and allylsulphocyanate strongly when exposed to the 

 action of chloroform. 



In the case of respiration-pigments we may suppose the chromo- 

 gens in the plant to be combined with sugar in the form of gluco- 

 sides. It is only after the action of the glucoside-splitting ferments 

 that the chromogen itself can be attacked and oxidised by oxydases. 



The same idea has been brought forward by Palladin under the 

 terra "prochromogen" -) which he applies to respiration-chromogens 

 in combination with sugar. In such a form they may be stored up 

 and are unaffected by the oxidising ferments. Through the action 

 of the glucoside splitting ferments the chromogens are freed and may 

 serve as oxygen carriers. Hence this combination with sugar may 

 be regarded as the inhibiting or retarding influence to an excessive 

 oxydation in the living plant. 



It is highly probable that anthocyanin formation, in the same 

 way, is dependent on both glucoside-splitting and oxydising en- 

 zymes. 



^) Armstrong, E. F., The simple Carbohydrates and the Glucosides. Also: 

 Mirande, M., Influence exercée par certaines vapeurs sur la cyanogenèse végétale. 

 Compt. rends. 1909. 



^) Palladin, W., Über Prochromogene der pflanzlichen Atmungschromogene. 

 Ber, d. d. bot. Gesellsch. 1909. 



Progressus rei botanicae III. 31 



