THE PLANT OXIDASES 221 



as was originally shown by Yoshida (1883). Without 

 asserting the identity of laccase with the phenolases met 

 with in other plants, it may be stated that its action upon 

 a number of reagents is qualitatively similar, hence there 

 is no objection to the use of the term provisionally. 



It has been pointed out by Bertrand (1896) that the 

 aromatic monophenols and monamines are not easily 

 oxidized by laccase, but that substances which it readily 

 attacks are all members of the benzene series containing 

 hydroxyl or amino groups in the ortho or para positions. 



Towards both heat and alcohol laccase is more stable 

 than is tyrosinase. Bertrand (1896, 2) was able to separate 

 these two enzymes, which exist together in Russula delica, 

 by precipitating a chloroform- water extract of the fungus, 

 in which equal weights of tissue and water had been 

 employed, by the addition of one and a half times its 

 volume of 95 per cent, alcohol. An aqueous extract of 

 the precipitate obtained ,from the alcoholic solution was 

 found to oxidize tyrosin, but had very little action on 

 hydroquinone or pyrogallol. The nitrate, however, when 

 concentrated at 50, still gave the laccase reactions, but 

 not those of tyrosinase. 



As was mentioned before, the phenolase so widely dis- 

 tributed in plant tissues is considered to consist of a 

 peroxidase and an organic peroxide. A great number of 

 experimentally ascertained facts can be satisfactorily ex- 

 plained on this hypothesis. For instance, sap pressed 

 from the leaves of Sambucus niger was found by the author 

 (1913) to turn a dilute guaiacum solution blue when tested 

 at once. On standing for two hours in diffuse light, this 

 power was lost, but the addition of a few drops of a neutral 

 four- volume solution of hydrogen peroxide resulted in the 

 appearance of the blue colour on testing. Again, the fresh 

 sap when boiled for two minutes failed to restore the 



