Atkins — Oxidases and their Inhihitors in Plant Tissues. 



323 



Discussion of Results of Table IV. 

 A general survey of the table leaves one with the impression that there 

 can be little connexion here between the intensity of natural anthocyan pig- 

 mentation and that of the peroxidase reactions. Evidently the amount of 

 chromogen is the controlling factor. In I. Xiphium the activity of the per- 

 oxidase is very great, yet over the yellow " signal " on the claw of the fall 

 there is in every case a sharply marked inhibition area, which remains un- 

 ooloured by tlie reagents, and as the plastid yellow goes into solution in the 

 treatment with alcohol, this region stands out very clearly. One cannot fail 

 to be impressed with the view tliat in tliis ease tlie peroxidase is concerned in 

 the production of antliocyan, for the limits of distribution of the former 

 coincide with that of the latter. In /. reticulata, however, deep pigmentation 

 occurs together with little or no oxidase activity. 



Table V. 



Miscellaneous. 



Discussion of Results of Table V. 

 In this table, too, there seems to be but little relation between peroxidase 

 activity and antliocyanin. /. tuberosa, known as the " Widow Iris " from 

 its almost black colour, contains large masses of solid pigment in the cell 

 vacuoles. Its small oxidase activity may possibly be accounted for by the 

 fact tliat the flower was a very old one, somewliat withered. 



The Effect of Darkness upon the Peroxidase Content of Flowers of Iris. 



Before concluding definitely that the reactions shown in the tables have 

 the meanings attributed to them, viz., that they are genuine expressions of 

 the properties of particular species and varieties, it is necessary to inquire into 

 the possibility that they may be in part due to differences in illumination. It 

 was sliown by Keeble and Armstrong that both organic peroxide and peroxi- 

 dase accumulate during darkness in certain plants. It was subsequently 



