114 REACTIONS INVOLVED IN [CH. 



conditions which are certainly not realised in Everest's experiments. 

 In this respect, the results obtained in vitro have no bearing upon the 

 reactions taking place in the plant. 



Hence the original hypothesis is not affected by Everest's criticisms. 

 First, it is quite conceivable that some of the hydroxyls of the chromogen 

 (flavone) remain unhydrolysed, so that all the products are in the 

 glucosidal state. Secondly, should this be disproved, there still remains 

 the alternative, suggested by Everest himself and not disproved by 

 his experiments in vitro, that the anthocyanidins formed in the plant 

 immediately recombine with sugar. There is no reason to believe 

 that the artificial reactions carried out by Everest at all reproduce the 

 course of events in the living plant. 



Apart from the similarity in distribution and reactions of flavones 

 and anthocyanins, evidence in favour of the glucoside hypothesis may 

 be collected and arranged under the following headings: 



1 . Evidence from results obtained in the cross-breeding of Antirrhinum. 

 These results will be discussed in greater detail in Part II, but a short 

 statement is necessary at this point, since the facts recorded are of 

 value in this connection. The original type of Antirrhinum has magenta 

 flowers, the colour being due to anthocyanin. During cultivation, two 

 varieties, among others, have arisen as sports, viz. an ivory, and a white, 

 both incapable of producing anthocyanin. Ivory, as the name suggests, 

 is ivory-white in colour, and has on the palate a spot of yellow which 

 is common to all varieties of Antirrhinum, except white. White is 

 dead white, without the yellow spot on the palate. When a white 1 

 is crossed with an ivory, a plant having magenta flowers like the type 

 is produced, and in these flowers, magenta anthocyanin is present 

 in the epidermis of the corolla. Hence the original ivory and white 

 varieties must between them contain the materials for the formation 

 of anthocyanin. It has been shown by Wheldale & Bassett 2 that 

 the pigment in the ivory variety is the flavone, apigenin: 



HO 



CO 

 which occurs in the plant as a glucoside. 



1 Of certain ancestry. See p. 161. 



2 Wheldale, M., & Bassett, H. LI., 'The Flower Pigments of Antirrhinum ma jus. 

 n. The Pale Yellow or Ivory Pigment,' Biochem. Journ., Cambridge, 1913, vn, pp. 441-444. 



