INHERITANCE OF COLOUR 243 



In other instances the aerial vegetative organs of many 

 varieties of plants, e.g. certain Chenopodiaceae, are charac- 

 terized by a red colour the presence of which is seemingly 

 independent, or nearly so, of external conditions. Thus 

 Salicornia ramosissima may be found in two forms, one apple 

 green and the other crimson, the intensity of which varies in 

 different years. In such cases there is good reason for sup- 

 posing that these colours are of an hereditary nature and 

 come true from seed. The same also appears to be true for 

 different forms of beet which are used for horticultural pur- 

 poses. On the other hand, in the familiar example of the 

 copper beech this is not so, the copper-coloured foliage, due 

 to the combined effect of a red cell sap and the green of the 

 chlorophyll, first originated, it is stated, as a sport and is 

 propagated by means of cuttings. 



In the case of anthocyan in flowers, much more definite 

 information is available owing to numerous investigations upon 

 the inheritance of colour in plants. And although questions 

 relating to genetics are outside our present scope, brief mention 

 may be made of certain facts in order to illustrate the inter- 

 relationship between this branch of botany and chemistry. 



In many plants the colour of the flowers depends on 

 various factors : — 



C, a chromogen which is not necessarily coloured, and 

 which is, in all probability, a glucosidal flavone. 



E, an oxidative enzyme, which acts upon C to produce a 

 red colour. 



e, another enzyme which acts upon the red pigment, due 

 to the action of E, and further changes it to another pigment 

 so that a different colour results. 



A, an antioxidase which inhibits the action of E. 



R, a reductase which neutralizes, as it were, the action of E. 



If a flower, say, of Lathyrus, only possesses C or E, then 

 the colour will be white or pale yellow, according to the colour 

 of the chromogen, if present. If the flower with the factor 

 C be crossed with a flower with the factor E, then the colour 

 of the flowers of the offspring will be red, or a deeper colour 

 if e also be present. If either A or R be present, then there 

 will be no difference in the flowers of the offspring as com- 

 pared with the parents, 



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