CH. vii] KEACTIONS IN FORMATION OF ANTHOCYANINS 105 



rapporter aux couleurs du prisme, que de chercher a connaitre la nature 

 des matieres colorantes elles-memes. Comme dans le prisme, le vert 

 tient le milieu et se trouve borde, d'un cote, par le jaune et le rouge, 

 et de 1'autre cote,, par le bleu et le violet, on croyait que le vert des 

 plantes etait de meme le point indifferentiel entre la serie de couleur 

 rouge-jaime et celle du bleu, et c'est par 1'oxygenation et la desoxy- 

 genation de la couleur verte, qu'on cherchait a expiiquer 1'origine de 

 ces couleurs, en se fondant sur des experiences chimiques incertaines, 

 sur des idees fausses d'oxygenation et de desoxygenation, sur Faction 

 des alcalis et des acides." A more correct point of view was reached 

 too by Leopold Gmelin (137) in 1828 1 ; he refused to accept the fact 

 that chlorophyll is reddened by acids, and that the products formed 

 from chlorophyll by acids, or naturally in autumnal leaves, again 

 become green with alkalies. He notes, also, that red autumnal leaves 

 contain both yellow chlorophyll, and a blue colouring matter which 

 is reddened by acids. 



Gmelin's criticisms, as well as others of the same kind, appear 

 to have been unconvincing; for again, in 1835, Clamor Marquart (5) 

 returns to the origin of anthocyanin from a metamorphosis of chloro- 

 phyll. Though objecting to the oxidation and deoxidation hypothesis, 

 he retains the idea of the formation of other pigments from chlorophyll, 

 this time, however, by addition and subtraction of water. By the 

 action of strong sulphuric acid, i.e. by subtraction of water from chloro- 

 phyll, a blue colouring matter 2 (anthocyanin) is obtained which turns 

 red with acids and green with alkalies. This blue substance, he says, 

 forms the basis of all blue, violet and red flower pigments. 



Marquart's evidence was thought to be insufficient by Von Mohl 

 (7, 8) ; for, with regard to the sulphuric acid reaction, the latter very 

 naturally remarks: "Si, dans ce cas, la couleur bleue doit annoncer 

 la formation artificielle de 1'anthocyane par la chlorophylle, il est 

 impossible de concevoir pourquoi, malgre la presence de 1'acide sulfurique 

 libre, la chlorophylle reste bleue et ne devient pas rouge." Also, with 

 respect to Marquart's evidence that cells which originally contained 

 chlorophyll, later contain anthocyanin, as for instance petals which 

 are primarily green, and then become blue or red. Von Mohl points 

 out, among other evidence, first, that anthocyanin is characteristic 

 of the epidermis while chlorophyll is found in the inner tissues ; secondly, 

 that chlorophyll may be found, apparently in no lessened quantity, 



1 Earlier edition than that in the Bibliography. 



2 This is of course, as we now know, a reaction given by plastid pigments. 



