CLASSIFICATION OF THE YEAST 



45 



the cell and the bud, elongates in the direction of this open- 

 ing and eventually pinches off a nucleus which migrates 

 into the bud. This rapidly increases in size and the open- 

 ing between the two cells soon closes. In a very young 

 bud the cell wall is either absent or very thin, but soon 



FIG. 31. MULTIPLICATION OF YEASTS BY BUDDING. 



develops, probably in all cases becoming evident before 

 separation from the mother cell occurs. 



Development of Spores. All species of true yeasts are 

 capable of producing spores under suitable conditions. 

 These conditions differ with the species. In most species 

 the spores are not developed in the ordinary cultural media 

 or by the usual methods. With many of the more common 

 yeasts of economic importance sporulation may be induced 

 by placing young vigorous cells under such conditions that 

 they will have an abundance of oxygen, plenty of moisture, 

 and the right temperature. This is most frequently accom- 



FIG. 32. DEVELOPMENT OF SPORES IN YEAST. 



plished by preparing small, flat gypsum blocks (plaster of 

 Paris). These are placed in deep Petri dishes, water 



