M. WlIELDALB 119 



against the hypothesis is that flavones, of tlie constitution indicated in 

 Fig. 2, are unknown. 



No reference is made by Willstatter to the pigments in the actual 

 red and purple varieties of the Corn-tlower. If the pigments of the 

 varieties are identical with the red and purple pigments found in the 

 blue type, we must sujjpose the factorial differences merely to affect 

 the acidity and alkalinity of the sap, the sap of the red variety being 

 acid, of the purple, neutral, and of the blue type, alkaline, which does 

 not appear to be a very reasonable suggestion. 



Grafe (13) also, working with flowers of scarlet Pelwrgonium, has 

 obtained an anthocyanin which forms very fine crystals, in combination 

 with acetic acid, of the composition, CisHosOis . 2CH3COOH. The 

 inheritance of colour in Pelargonium has not yet been investigated, 

 so that these results cannot be brought into use at present. 



Factors involved in the Formation of the Anthocyanin pigments. 



The next question to be considered is the nature of the factor, R, 

 connected with the formation of anthocyanin. 



It was originally suggested (Wholdale, 30), that the R factor might 

 be an oxidase and that the formation of anthocyanin might be repre- 

 sented as : 



glucoside + water ±^ flavone + sugar 



X (flavone) + oxygen — *- anthocyanin 



the first reaction being controlled by a glucoside-splitting enzyme, the 

 second by an oxidase. 



Since the views in connection with oxidases and oxidase reactions 

 are very confusing, a short statement, as regards the action of oxidising 

 enzymes, may not be out of place at this point. 



It has long been known that solutions of certain compounds, such 

 as guaiacum, a-naphthol, and benzidine are oxidised to coloured products 

 in the presence of plant extracts. The water extracts, for instance, of 

 some plants when added to guaiacum tincture at once produce a blue 

 colour (direct oxidase reaction). Extracts from other plants do not 

 produce this blue colour, unless hydrogen peroxide is also added 

 (indirect oxidase reaction). If a comprehensive examination be made 

 with these tests (Clark, 7, 8 ; Wheldale, 31), it will be found that the 

 members of many orders and genera {Umhelliferae, Labiatae, Boragina- 

 ceae and others) commonly give a direct action whereas the members 



