RELATIONSHIP BETWEEN A RED TORULA AND A MOLD. 155 



ism appeared and nothing even resembling the thick yellow 

 growth in the original fly bottle could be seen. 



Other fly bottles were obtained, and finally, from one of these, 

 a growth was obtained which had the typical yellow color and 

 the leathery texture. Upon replating this growth repeatedly, 

 however, nothing could be obtained except the ordinary yeast 

 and the mold. 



After repeatedly smearing such material over plates and getting 

 only the mold and ordinary yeast referred to, a final survey of 

 all plates heretofore made was undertaken with a view to dis- 

 carding most of them. 



During this survey, however, there was noted on one of the 

 older plates several tiny colonies having a distinct, coral-red 

 color. One of these was fished to Saboraud's agar and held at 

 room temperature for three days. During this time there ap- 

 peared a soft, creamy, coral colored growth, which, upon micro- 

 scopical examination, was found to be a yeast or torula. It was 

 later shown that this red torula occurred as a contaminant in 

 cakes of the commercial yeast referred to above. After three or 

 four more days, the pink growths on the plates from which the 

 pink colony had been fished, were observed to be gradually turning 

 yellow in places, and wherever the yellow color appeared there 

 was also a growth of the mold. The yellow growth had also 

 become tough and leathery. Smears made from these colonies 

 showed the presence of a mass of yeast cells matted and closely 

 bound together by mold hyphse. It appeared that the combined 

 growth of the red torula and the white or unpigmented mold 

 produced the bright lemon-yellow color, and the tough character 

 of the colonies. It only remained to get pure cultures of the two 

 organisms growing under controlled conditions to decide this 

 point. This was easily done by inoculating one side of a plate 

 with a pure culture of the mold and the other half with a pure 

 culture of the red torulse. The plate was held at about 22 C. 

 for four days and good growth of both organisms occurred. The 

 two growths remained separate for some days, but soon the 

 spreading mold began to overgrow the area streaked with the 

 torulze. Wherever the mold encountered a colony of the torulae, 

 the colony became yellow, hard and tough. 



