PEOF. H. M. WAED AND MISS E. DALE ON CEATEEOSTIGMA PUMILUM. 34.9 



I. The cyanic series has for its type the red substance occurring in solution, and 

 includes the blue, violet, and " carmine red " colours derived from it. The colours in 

 this series all become red with acids and blue with alkalies. 



II. The type of the xanthic series is the solid yellow colouring-matter either contained 

 in or derived from plastids (leucites), together with orange-yellow, orange-red, and brick- 

 red solid pigments. 



When treated with concentrated sulphuric acid, these bodies all become indigo-blue 

 of varying degrees of brightness. With iodine they all take on a green colour. All of 

 them are insoluble in water. 



The pigments of the xanthic series may be further divided into two groups with 

 reference to their behaviour towards other reagents : — 



a. Yellow pigments (xanthin of some authors). — These, according to Courchet, are 

 never crystalhne, nor can crystals by any means be obtained artitici<illy from their 

 solutions. They are slightly soluble in chloroform, benzine, and ether, but most soluble 

 in alcohol. Before becoming blue with concentrated sulphuric acid they pass through 

 an intermediate green stage, which may be due to a mingling of the pigment which has 

 become blue with that which is still yellow. 



|S. Orange-yellow a?id 07^ange-red pigments may be amorphous, or in the form of 

 crystallites or crystals. They are most soluble in ether, benzine, and chloroform, and 

 less so in alcohol. With concentrated sulphuric acid they pass through a violet or 

 violet-red phase, probably on account of the mixing of blue and red colouring-matter. 



These differences may be tabulated in the following way : — 



Yellow Figments. Orange-yellow and orange-red. 



Non-crystalline. Amorphous, crystallites, or crystals. 



, chloroform. f chloroform. 



Slightly soluble in I benziue. Most soluble in I benzine. 



i ether. '- ether. 



Most soluble in alcohol. Less soluble in alcohol. 



With concentrated sulphuric acid, first green, "With concentrated sulphuric acid, first violet 



then blue. or violet-red, then blue. 



The colouring-matter of the flowers of Aloe is so peculiar in its reactions that it was 

 placed by Courchet in a group by itself. It occurs in the form of chromoplasts (chromo- 

 leucites) consisting of a coloured stroma, which is apparently homogeneous and contains 

 very distinct pigmentary granules. With concentrated sulphuric acid the colour changes 

 into a greenish yellow, but there are slight differences in this reaction due to the original 

 colour and to the physical condition (whether crystalline or amorphous) of the pigment. 

 Alkalies cause the formation of orange-coloured drops. In ether and chloroform the 

 colour is almost insoluble ; in alcohol it is very soluble, and forms a solution which 

 Courchet describes as " currant-red." 



The reactions of the red colouring-matter in the root of Craterostlgma in some respects 

 resemble those of the pigments of the xanthic group, ha others those of the colour in 

 -4io^-flowers, while in others again they are peculiar. 



