THE OXIDASES IN RELATION TO PIGMENTATION 281 



authors also demonstrated that anthocyanin appears in 

 red cabbage even in the dark. 



An increase in the carbohydrate content of many 

 leaves, leading to the production of anthocyanin, was 

 ingeniously effected by Combes (1909). The method 

 adopted was to insolate them, and to prevent the transloca- 

 tion of the assimilates by ringing the stem. 



Molliard (1909) allowed the development of radishes to 

 take place in sugar solutions, and found that a red cell sap 

 was only formed in those portions which were near the 

 surface. This he explains as being due to the lack of 

 sufficient oxygen in the deeper portions of the culture 

 medium. 



The action of insects upon vegetable tissues, giving rise 

 to hypertrophy and red pigmentation, has been investigated 

 by Mirande (1907). In such pathological conditions as 

 arise from these lesions he was able to demonstrate an 

 accumulation of sugars, tannins, and oxidases. 



All the above researches seem to point to one conclusion 

 that in plants which can produce anthocyan pigments 

 the presence of a sufficient supply of sugar is a necessity. 

 Whether this condition is realized by the mobilization of 

 the reserves of seeds, by photosynthesis, by employing 

 sugary culture media and increasing the permeability of 

 the cells by strong illumination, or by decreasing the 

 intensity of respiration by exposure to cold, is after all 

 immaterial. The careful quantitative study by Combes 

 (1909) of the relation between the carbohydrates of various 

 leaves, such as Ampelopsis hederacea, and the production 

 of red pigment, has finally proved the great importance of 

 an abundance of sugars. A good illustration of this has 

 been pointed out by Dixon, who observed that small 

 branches of Ribes rubrum, removed from the bush before 

 the opening of the flowers in early spring, bear only white 



