vi] INFLUENCING THE FORMATION OF ANTHOCYANINS 97 



instance, tartaric, salicylic, citric and oxalic, on the contrary, appeared 

 to slow down the formation ; to this tannic acid formed an exception, 

 since the reddening appeared more quickly in its presence. 



Although anthocyanin was produced in the cultures in the dark, 

 Katie found that the development was always earlier in the light. As 

 regards temperature, it was found that 25 C. was the optimum for the 

 appearance of the pigment in the light and 28 C. in the dark. 



The absence of carbon dioxide had no effect on the formation of 

 anthocyaniu in sugar solutions, except in the case of glycerine, where 

 the development was weaker. Oxygen, on the contrary, was found to 

 be necessary for the reddening. 



Katie made further observations with a number of other plants, 

 and although his experiments are described in great detail in his disser- 

 tation, no more than a short statement will be given here as they were 

 largely on the same lines as those with Hydrilla. 



Elodea canadensis. In -26-1 % cane sugar there was a slight colora- 

 tion in the light, but none in the dark ; in 1 % grape sugar there was 

 colour both in the light and in the dark. In the case of cane sugar the 

 development was increased by addition of potassium nitrate and calcium 

 sulphate. 



Hydroclmris Morsus-ranae. In cane sugar and laevulose some 

 pigment appeared in the dark; in grape sugar and maltose, there was 

 none in the dark. 



Sagittaria natans. In 5 % cane sugar there was a considerable 

 development of colour, but only in the light. 



Allium Cepa. The colourless scales of a variety which normally 

 contained some anthocyanin turned red in sugar solution ; a white 

 variety, however, produced no colour under any conditions. 



Canna indica. Etiolated leaves in 5-15 % cane sugar formed pig- 

 ment. 



Veronica Chamaedrys. In sugar cultures colour only developed in 

 the light and was located in the epidermal cells. 



Rosa 'Marechal Niel.' Green leaves, or pieces of leaves, in 15% 

 cane sugar formed colour only in the light. It was found in both 

 epidermis and spongy tissue. 



Saxifraga cordifolia. Pieces of a leaf in 5 % cane sugar only gave 

 a good development of anthocyanin in the light. 



Pittosporum (undulatumt). Green leaves and pieces of leaves in 

 5-15 % cane sugar formed pigment only in the light, and it was found 

 to be located in the inner tissues and not in the epidermis. 



w. P. 7 



