260 E. B. FRED AND W. H. PETERSON 



95.6 are a salmon shade of pink and 85.1 is a magenta shade. 

 In form these organisms vary from round to oval, but elongated 

 cells were the most abundant. 



Factors that inflitence color 



Oxygen. The influence of oxygen on the production of pig- 

 ment by these yeasts was determined by growing the cultures 

 in the air, and in a desiccator where only a limited supply of air 

 was available. In the presence of air the growth and pigment 

 production was good while in its absence a fair growth and no 

 color was obtained. When these colorless tubes were exposed 

 to the atmosphere a sahnon-pink color developed rapidly usually 

 within one to two days. The influence of oxygen was also noted 

 when kraut was exposed to the air, e.g., pale pink kraut turned 

 a deeper color after a few minutes exposure. 



Reaction. The reaction of the medium for cultivating these 

 organisms was varied between the pH values of 6.5 and 7.2. 

 Pigment was formed in all cases and approximately to the same 

 extent. At a reaction of 5.5 the growth was not so rapid, but 

 the color was somewhat more brilUant. 



Temperature. The influence of this agent on color formation 

 by these yeasts was studied at 18°, 22°, 28°, and 37°C. Only 

 a very scanty growth was noted at 37°C, a profuse growth at 

 22° and 28°C, and a fair growth at 18°C. The deepest pigment 

 was found in the tube cultures at 22°C. and next in intensity of 

 color, at 28°C. Although the higher temperature of 28°C. re- 

 sulted in a profuse growth the pink color was not nearly so 

 noticeable as at lower temperatures. Apparently about 22°C. 

 or 71°F. gave the most marked color. 



Iron and manganese salts. The influence of iron citrate, 

 iron ammonium citrate, iron lactate, iron sulphates, and man- 

 ganese sulphate, on pigment formation was studied. A decided 

 difference in behavior of the various strains of yeast towards the 

 iron and manganese compounds was noted. Strain 85-1 re- 

 sponded far more to the iron salts than either strain 24-1, or 

 95-6. Of the various compounds, iron lactate proved the best 

 stimulant forpigment production. The other compounds, e.g., 



