THE OXIDASES IN RELATION TO PIGMENTATION 277 



addition of salts of alum, barium, or zinc ; this is analogous 

 to the formation of aluminium salts or lakes by anthocyanin 

 as obtained by Miyoshi (1900) and Grafe (1911). The colour 

 of Peche's pigment was destroyed by the addition of sodium 

 hydrogen sulphite, and restored by acidifying in a manner 

 similar to natural anthocyanin as shown by Grafe. 



Tswett (1913, 1914) states that in apples, pears, white 

 grapes, pulp of red grapes, bananas, petals of Rosa and 

 Cyclamen, alcohol-soluble tannin-like substances are present 

 which yield colouring matters similar to anthocyanin 

 when treated with strong mineral acids in presence of 

 formaldehyde or acetaldehyde. In other tissues, such as 

 the leaves of white cabbage, mesophyll of red cabbage, 

 Pelargonium leaves, carrots, and potatoes, these tannin- 

 like substances are wanting, and no coloration of this 

 type was produced. Artificial colouring substances of this 

 class agree with natural anthocyanins, not only in their 

 absorption spectra, but also in their chemical reactions, 

 being either decolorized or altered in colour by alkalies and 

 acids, and being decolorized by the aldehyde reagents, 

 sodium hydrogen sulphite, phenylhydrazine, and hydrogen 

 cyanide. 



In this connection, the researches of Combes (1911, 1 and 

 2; 1914) are of interest. He comments on the facts that 

 though, as shown by Mirande (1907), the quantities of 

 tannins, of glucose, and of oxidase, are greater in coloured 

 tissues than in those free from anthocyanin, and though 

 he had himself pointed out the influence which abundance 

 of carbohydrates has upon the production of anthocyanin, 

 yet no direct relationship has, in his opinion, been proved 

 between the presence of these substances and the contem- 

 porary formation of the pigment. Combes considers that 

 if anthocyanin formation takes place in a tissue as the fina 

 result of an uninterrupted series of changes, it should be 



