334 MICROCHEMISTRY OF PLANT PRODUCTS 



changed to a blue color by the action of concentrated sulphuric 

 acid. 



Anthocyanins. — These are coloring matters of flowers, 

 leaves, and other parts of plants which impart red, violet, blue, 

 blue-green, or green colors, the character of the color being 

 dependent on the alkalinity or acidity of the cell-sap. The 

 anthocyanins are soluble in water, alcohol, and ether, and are 

 decolorized in strong alkalies. 



Anthoxanthin. — This yellow coloring matter in the chro- 

 moplasts of flowers and fruits takes on a blue color with con- 

 centrated sulphuric acid. Since the chromoplasts of flowers 

 and fruits were first of all green, anthoxanthin is probably a 

 derivative of chlorophyll. Anthoxanthin is also called xanthin 

 and xanthophyll. 



Arabin. — This is the gum derived from species of Acacia 

 and known as gum arable. Arabin is soluble in hot and cold 

 water, and insoluble in alcohol and ether. The aqueous solu- 

 tion will mix with glycerine, but concentrated glycerine has 

 little effect on the hard gum. 



Asparagin, C^HgNH^.CONH^.COOH.— This is a nitrog- 

 enous compound of simpler constitution than proteids. It 

 is formed within plants both analytically by the decomposition 

 of proteid, and synthetically probably by the combination 

 of simpler substances. Asparagin is soluble in water and in 

 the cell-sap, and is one of the most important nitrogenous com- 

 pounds capable of solution and circulation within plants. It 

 combines with non-nitrogenous compounds to form proteids, 

 and is apt to accumulate in those parts of plants where there 

 is not sufficient non-nitrogenous material at hand for the 

 formation of proteids. The accumulation of asparagin is par- 

 ticularly apt to occur in plants which are grown in the dark, 

 so that carbon assimilation does not take place. Thus, Pfeffer 

 found that when seedlings of lupin were grown in the dark, 

 they contained a large amount of asparagin, but when they 

 were brought to the light, the asparagin disappeared. He 

 found that this was not due simply to the influence of the light. 



