16 BULLETIN 819, U. S. DEPARTMENT OF AGRICULTURE. 



smaller quantity than on solid media. When grown at refrigerator 

 temperature no pigment is produced until the fourth or fifth day, 

 and then only a very slight amount. The pigment is not red or rose- 

 colored, as the name " red Torula " or " red yeast " often given to 

 the organism by investigators would indicate, but is more nearly the 

 color of the ordinary pink coral. Its color matches the Orange Red 

 Tint No. 1 of the Bradley educational colored papers. Chapman 

 (1916) , who studied the coloring matter of " red Torulae," has found 

 it to be a substance similar to carotin. In the present investigation 

 of the pigment of the yeast an attempt has been made to determine 

 first a method of dissolving it, and, second, its solubility in various 

 substances. After several experiments with different methods the 

 following manner of dissolving the pigment has been found most 

 productive of results. The yeast was grown on large agar slants for 

 3 days at room temperature, at the end of which time the growth was 

 transferred to a small mortar and thoroughly ground with fine sand 

 to break the yeast cells. After grinding with the sand the mixture 

 was kept at about 40° C. until completely dried, and then ground 

 again with the solvent to be tested. The mixture was filtered, and if 

 the pigment was soluble the filtrate obtained was of a clear pink color. 

 Using this method, it has been found that the coloring matter is 

 insoluble in hot and cold water,, is slightly soluble in alcohol and car- 

 bon disulphid, somewhat more soluble in chloroform, and very 

 soluble in ether. As such solutions of pigment slowly lose their color 

 upon standing in the light, at the end of 2 weeks the chloroform and 

 alcohol solutions were colorless. Ether solutions left standing in the 

 light for 1 month are completely decolorized. 



PHYSICAL FEATURES OF THE PINK YEAST. 



RELATION TO OXYGEN. 



Five methods were used in studying the growth of the pink yeast 

 under anaerobic conditions. 



Method 1 {Hesse's method) . — Stab cultures were made in dextrose 

 agar, choosing for the purpose a straight tube containing a deep 

 column of medium and thrusting the inoculating needle to the bot- 

 tom of the tube. A layer of sterile paraffin oil, 1 to 2 cm. deep, 

 was poured on the surface of the medium, and the culture was in- 

 cubated at room temperature with a control tube of agar which had 

 not been inoculated. 



Method 2. — A tube of agar was liquefied by heat, poured into a 

 sterile Petri dish, and allowed to solidify. The surface of the medium 

 was inoculated with the pink yeast in one spot only, A cover slip 

 was taken from a jar of alcohol with sterile forceps, and the alco- 

 hol burned off in the flame. The sterile cover slip was lowered on 

 the medium over the inoculated spot, carefully excluding air bub- 



