272 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



Pelargonin, obtained from Pelargonium, affords two 

 molecules of glucose and one of pelargonidin, the hydro- 

 chloride of which has the following formula: C 15 H 11 6 C1. 

 Heating with alkali in this case gives rise to phloroglucinol 

 and p-hydroxybenzoic acid. 



Delphinin, from Delphinium, when hydrolyzed, gives two 

 molecules of glucose, two of ^>-hydroxybenzoic acid, and 

 delphinidin. The hydrochloride of this body has the com- 

 position C 15 H 11 7 C1. Treatment of the latter with alkali 

 breaks it up into phloroglucinol and gallic acid. 



Another crystalline anthocyanin has been isolated from 

 grapes. It is known as cenin, and forms a picrate which 

 crystallizes in red prisms. (Enin is a monoglucoside of 

 cenidin, prepared as the hydrochloride C 15 H 15 7 C1. 



The pigment of the bilberry, too, myrtillin, has been isolated 

 in the pure state. It is a glucoside of an anthocyanidin 

 which is also present in the anthocyanin of Althea rosea. 



In the same paper Willstatter and Mallison deny that 

 the coloured products obtained by the reduction of 

 morin, luteolin, quercetin, and other flavones, or of the 

 yellow pigment of Ampelopsis hederacea, can be considered 

 as anthocyanins. In a later paper (1914, 2), however, they 

 describe the production of allocyanidin, and cyanidin in 

 small quantity, by the reduction of quercetin. [See p. 292.] 



The relationships of the various anthocyanins may 

 perhaps be rendered plainer by the following scheme: 



Source of Anthocyanin. Anthocyanidin and Other Products. . 



Cornflower, flower (cyanin) . . Cyanidin and glucose, two molecules. 

 Rosa gallica, flower . . . . Cyanidin and glucose, two molecules. 



Cranberry, fruit . . . . . . Cyanidin and galactose, one molecule. 



Pelargonium, flower (pelargonin) Pelargonidin and glucose, two mole- 

 cules. 

 Delphinium, flower (delphinin) Delphinidin, glucose two molecules, 



and 2>-hydroxybenzoic acid, two 



molecules. 



Grape-skins (oanidin) . . ... (Enin and glucose, one molecule. 

 Bilberry, fruit (myrtillin) . . Myrtillidin and glucose. 



