F. Keeble and E. F. Armstrong 307 



continuous using up of oxydase in the production of new pigment to 

 replace that which, for all we know, may be continuously destroyed when 

 the plant is exposed to light. It is a well known fact that conditions of 

 illumination influence the amount of anthocyan pigment which occurs 

 in a plant. For example, it is a common practice among horticulturists 

 to enclose choice fruits such as grapes and apples in translucent paper 

 bags and it is claimed that this expedient, beside protecting the fruit 

 from insects, improves its colour. This, if true, would point to the con- 

 clusion that light of high intensity exercises a destructive influence on 

 anthocyan pigment. 



...ft**. ^, 



Ai A., B, B., 



4 A. 4B. ■ 



Fig. 4. (From photographs.) The effects of Light and Darknes.s on the Peroxydase of 

 Primula sinensis. 



Ai and Bi, normally illuminated plants. 



J.) and B-,, plants kept in darkness for 48 hours. 



A. A double, light magenta plant (8/2/2/11) : flowers treated with benzidine 



and hydi-ogen peroxide. 



B. A white magenta-flaked plant of Mt Blanc Star: flowers treated with 



a-naphthol and hydrogen peroxide. 



The most casual observations in the garden show that the depth of 

 colouration of flowers varies considerably during the course of develop- 

 ment of the flower. Thus the petals of many varieties which are white 

 in the mature stage are pink or pinkish in the bud stages and it is 

 po.ssible that we have in such instances an example of the pigment 

 ■destroying action of light. 



Although an adequate discussion of the facts just recorded would be 

 out of place in the present communication, it will be evident that if they 

 are shown to be true generally these facts may have an important 

 bearing on many phenomena other than those connected with the pig- 

 mentation of plants. For if we ascribe to oxydases a general role in the 

 metabolism of the plant as well as a special function in pigment pro- 

 duction, the fact that the oxydase content of plant tissues waxes in 

 darkness and wanes in the light may have bearings on the phenomena 

 of periodicity which are at once such puzzling and general attributes of 

 the Vegetable Kingdom. The work of Palladin (1911) and others 



