226 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



with 0-002 N potassium permanganate in presence of 

 dilute sulphuric acid till completely colourless. 



The results are recorded in the table which follows. 

 In the lower row of permanganate numbers are the figures 

 obtained after the addition of 1 c.c. of 0-05 per cent, 

 hydrogen peroxide solution to each tube at the same time 

 as the tyrosin was poured in. 



TABLE LVI. 



EFFECT OF ADDITION OF HYDROGEN PEROXIDE. 



It may be remarked that the amount of hydrogen peroxide 

 added is all, or almost all, used up in the reaction with the 

 enzyme; consequently, as, indeed, is shown by Column I., 

 the increase in permanganate required is not due to inter- 

 action of the latter with peroxide. 



Further evidence of the complex nature of tyrosinase 

 was obtained by Bach (1908, 1), for on shaking a solution 

 of the enzyme with magnesium carbonate, it was without 

 action on tyrosin till after the addition of peroxide. Thus 

 treatment with the carbonate must have removed the 

 peroxide constituent of the oxidizing system. 



It is still uncertain, however, whether the action of 



