278 Oxydases and Pigments of Plants 



other workers, the modes of inheritance of colouration are known with 

 detailed accuracy in many species. This rapid advance has stimulated 

 enquiry into the chemical aspect of the phenomena of pigmentation, 

 and the investigations of Miss Durham (1904), Palladiu (1908), Combes 

 (1910), Miss Wheldale (1910) and Gortner (1910) have resulted in the 

 production of a large body of evidence in fixvour of the current 

 hypothesis that pigmentation is the outcome of the action of oxydase 

 on chromogen. 



We propose in the present communication, some of the results of 

 which have been published in abstract form elsewhere (Keebie and 

 Armstrong, 1912), to present further and as we think convincing 

 evidence in favour of this hypothesis, to describe the distribution of 

 oxydases in Primula sinensis and certain other plants, to produce 

 experimental evidence of the fact that the pigment-forming activity of 

 oxydases may be inhibited in various races of plants (Dominant White 

 races) and to show that the oxydase-content of a plant is modified by 

 such external conditions as light and darkness. 



Tlie Role of Oxydase in Pigment Formation. 



Inasmuch as the literature relating to oxydase is very extensive 

 and has been summarised recently in monograph form by Kastle (1909) 

 and by Clark (1911) we need do no more here than state briefly the 

 hypothesis of Bach and Chodat, the acceptance of which is implied in 

 the present communication. 



This hypothesis holds that an oxydase is of a dual nature. The 

 constituents of an oxydase are a peroxydase and a peroxide. The 

 peroxide behaves as an activator to peroxy-dase in the sense that it 

 supplies the latter with oxygen which may then be transferred to an 

 oxidisable body. This activating action may be effected by hydrogen 

 peroxide. The nature of tlie peroxides of the plant is unknown. 



Peroxydases are classed generally with enzymes ; they differ, however, 

 from hydrolytic enzymes in that they undergo destruction, at least in 

 vitro, in consequence of the exercise of their oxidising function. 



There seems reason to believe that iron, manganese and other 

 elements in combination with oiganic substances play some part as yet 

 obscure in the oxidation processes of the plant. 



The hypothesis that oxydases are concerned in the formation of 

 plant-pigments was first suggested by Pick (18>S3), and evidence in 

 favour of this hypothesis has been put forward by many observers — 



