1913.] 



Anthocyan Pigments of Plants. 



321 



2. The behaviour of flowers of Brompton stocks, as described in detail in 

 Part IV of this series, provides a convincing proof that it is possible for all 

 the mechanism for colour production to be present in a flower, and yet for 

 the bodies concerned not to interact to produce pigment until the plasmatic 

 impermeability has been destroyed. 



The fading and recovery of colour of petals of these plants was observed 

 by the present writer during the preliminary experimental work in connec- 

 tion with the above paper. The facts will be referred to here only in so far 

 as they illustrate the point at issue. 



If coloured flowers of Brompton stocks are soaked in absolute alcohol, the 

 contained pigment gradually fades; on transferring the colourless petals to 

 water they quickly become coloured, the " recovered colour" being of exactly 

 the same shade as that of the fresh flower used. 



In the paper referred to evidence is presented that the fading of the 

 coloured petal in alcohol is due to the reduction of the pigment to a colour- 

 less state, as well as to its diffusion out into the surrounding liquid, and that 

 the formation of pigment when the petal is transferred to water is the result 

 of an oxydase converting into pigment a colourless chromogen substance 

 contained in the petals in addition to a re-oxidation of the reduced pigment 

 remaining. 



Thus, in stock, oxydase and chromogen are both present, and the condi- 

 tions are naturally such as to allow a proportion of these two bodies to come 

 together to produce pigment. In the white-flowered variety of lychnis 

 coronaria the natural conditions are never such as to allow any interaction 

 between oxydase and chromogen. On treatment with alcohol the barrier is 

 removed by the destruction of the plasmatic impermeability, and, as a result, 

 pigment is produced. 



The method which serves in the case of Lychnis to bring chromogen and 

 oxydase together, and causes them to interact with one another, serves 

 with Brompton stocks to bring about a large increase in the amount of 

 pigment present — which pigment is of the same colour as that occurring in 

 the flower under natural conditions. 



By use of such methods the following types of white flowers have been 

 demonstrated in the course of this investigation : — 



1. White Floivers which contain an Oxydase and a Chromogen, e.g. Lychnis 

 coronaria, Anemone japonica, Chrysantheniuni sp. — When petals of these 

 plants are subjected to the action of alcohol, chloroform, etc., a colour change 

 is produced. The colour may be brown, as in Anemone japonica, and appear 

 more or less evenly all over the petal ; or of a reddish tinge, as in Lychnis 

 coronaria, where, the colour is located chiefly in the veins. In both these 



