THE OXIDASES IN RELATION TO PIGMENTATION 253 



of flavones which resemble anthocyanins and antho- 

 cyanidins in many of their qualitative reactions. Whel- 

 dale (1915), on the other hand, points out that in the 

 absence of analytical data it is not possible to accept their 

 evidence as conclusive, and also that the body obtained 

 by reducing apigenin, which occurs in Antirrhinum, with 

 nascent hydrogen, in no way resembles the Antirrhinum 

 anthocyanin. Furthermore, the latter contains a higher 

 percentage of oxygen than does apigenin. 



The researches of Wheldale being primarily concerned 

 with problems of genetics, her further work was directed 

 to the study of the anthocyanins rather than to that of 

 the oxidase system, for the universal presence of some 

 enzyme of this type at once excludes it from acting as a 

 Mendelian unit character. These sap-soluble pigments 

 will be referred to in a subsequent section. 



MlCROCHEMICAL AND GENETIC RESEARCHES ON OXIDASE 



DISTRIBUTION. 



Though the above reasoning, based on the widespread 

 occurrence of oxidases, is undoubtedly true, researches by 

 microchemical methods upon the distribution of oxidases 

 and inhibitors in tissues have not been without fruit, as 

 is shown by the results obtained by Keeble and Armstrong 

 (1912). These authors employed a-naphthol and benzidine 

 as reagents, and found that whereas in flowers the epidermis 

 and veins oxidized the latter to a brown substance, fre- 

 quently deposited as crystals, yet a-naphthol was only 

 oxidized to a lavender tint in the veins, the slight shade 

 of colour sometimes occurring elsewhere being negligible. 

 (In passing it may be pointed out that very feeble oxidation 

 of benzidine causes the appearance of a blue colour.) Ac- 

 cordingly, in their earlier papers they refer to " epidermal " 

 and " bundle " oxidases. This distinction appears in their 



