12 INTKODUCTOKY [OH. 



anthocyanin also is localised. A further point of interest was discovered 

 in connection with certain varieties of Primula known as dominant 

 whites. These varieties have pigment (anthocyanin) in stems and 

 leaves, though the flowers are white, and they are regarded, from their 

 behaviour in crossing, as coloured forms in which the flower-colour 

 is inhibited by some factor present in the plant. Keeble & Armstrong 

 were able to show that flowers of these varieties gave ordinarily no 

 oxidase reaction, but after treatment with certain reagents, the inhibitor 

 was removed, and the oxidase reaction appeared in the petals. On 

 the other hand, they found that the true albinos in Primula gave the 

 oxidase reactions as well as the coloured varieties. Hence to make 

 the hypothesis fit the case of Primula, they were obliged to assume the 

 lack of colour in the true albino to be due to lack of chromogen, an 

 assumption which has never been verified. 



Meanwhile the author's investigations on Antirrhinum proceeded on 

 the lines of isolation and analysis (244) of the pigments of the colour- 

 varieties. These pigments were prepared on as large a scale as possible 

 by making water extracts of the flowers, precipitating the pigment as 

 a lead salt by lead acetate, and again decomposing the salt with sulphuric 

 acid. Filtered from lead sulphate, the pigment was obtained in dilute 

 acid solution. It had been previously ascertained that anthocyanins 

 are largely present in the plant in combination with sugar as glucosides. 

 On boiling with acid, the glucoside is hydrolysed and the pigment, 

 which is less soluble than the glucoside, separates out. This method 

 was adopted for obtaining the pigment from the acid solution. The 

 pigment of the ivory variety of Antirrhinum was identified by Bassett 

 and the author with apigenin, a flavone of known constitution occur- 

 ring in Parsley (Apium Petroselinum). Of the anthocyanin-containing 

 varieties of Antirrhinum there are two, red and magenta, analogous 

 to the red and purple varieties of Lathyrus and Matthiola. Analyses 

 were made (254) of the red and magenta pigments prepared separately 

 from several different varieties, and the results were concordant. In 

 the case of both pigments the percentage of oxygen was greater than 

 that in the flavone apigenin. Determination of the molecular weights 

 of the red and magenta pigments, though not obtained to a high degree 

 of accuracy, indicated that the molecules of anthocyanin are consider- 

 ably larger than those of apigenin. 



The conclusions drawn by Bassett and the author (254) were that 

 in Antirrhinum the anthocyanins are derived from the flavone apigenin 

 by oxidation, accompanied by condensation, possibly of two flavone 



