Varietäten, Descendenz, Hybriden. 105 



the Mendelian Factors for Colour in Plants. (Rep. Evol. 

 Comm. Roy. Soc, London. V, p. 26—31. 1909.) 



The authors experiments show reasons for regarding the numerous 

 colour-varieties of Stocks and Sweet Peas as terms in a series of 

 oxidation-processes. In these plants all the non-anthocyanic varieties, 

 i. e. whites and creanis, have been found to contain a colourless 

 chromogen of the nature of a flavone; the coloured varieties contain 

 this chromogen in a State of oxidation. Hence the loss of power to 

 produce colour in these whites and creams is not due to the absence 

 of chromogen, and some other cause for albinism must be sought. 

 The alternative of connecting lack of colour with loss of an oxidising 

 ferment ied the author to test the flowers for oxydases. 



An oxydase may be represented as a system of peroxide- 

 peroxydase. The System as a whole is capable of blueing guiacum 

 tincture (direct action), while the Peroxydase alone requires the 

 addition of hydrogen peroxide in order that the blue colour may 

 be produced (indirect action). Acting upon this view the extract of 

 the flowers of several varieties of Stocks and Sweet Peas was tested 

 by the addition of guiacum tincture alone or together with hydrogen 

 peroxide. 



All coloured varieties of both genera were found to give some 

 direct action and a strong indirect action, Extracted Fi whites in 

 both genera gave direct and indirect reactions in different degrees 

 of intensity. Among the whites from a rose Stock, throwing rose, 

 flesh and white, individuals were found which gave a strong indirect 

 action while others gave a weak, the proportion of strong to weak 

 being about 3:1. Whites from a crimson Stock, throwing crimsons 

 and whites only, all behaved alike. 



The results may be interpreted on the assumption that the fol- 

 lowing bodies are involved in the production of flower-colour: — 



(1) An organic substance (X) capable of functioning as a peroxide. 



(2) A Peroxydase acting upon the peroxide with the production of 

 active oxygen. (3) A second ferment or activator reoxidising the 

 peroxide. (4) A chromogen (C) capable of oxidation by means of the 

 oxygen set free by the Peroxydase. (5) The oxidised chromogen or 

 anthocyanin. 



On this supposition, albinism might result from the loss of the 

 power to produce either the Peroxydase or the activator ferment, 

 since in either case the mechanism for transferring oxygen from 

 the air to the chromogen would be incomplete. There would thus 

 be two forms of albino which, mated together, would give coloured 

 offspring. (In Antirrhinum albinos exist from which the chromogen 

 is absent, in addition to those which contain the chromogen but 

 lack the complete oxidising-system). 



The factors for colour may then be represented as A, activator 

 and P, Peroxydase, the two, in combination with a peroxide X,, 

 forming an oxydase System capable of acting on the chromogen, C, 

 with the production of red anthocyanin. Blueish-red and purple forms 

 of anthocyanin must be represented as due to the action of additional 

 blueing oxydase upon the product of the action of A,Pi, though 

 the former is unable to act directly upon the unaltered chromogen. 

 The blueing oxydase may be represented as Aj activator, P^ Peroxydase, 

 and X, peroxide. 



The existence in Stocks of dilute varieties, such as flesh, rose 

 etc. depends upon an additional reducing factor, which prevents 

 the whole reaction from taking place. Extracts from these varieties 



