FORMATION OF SPORES IN YEAST. 



187 



lias begun to produce daughter-cells in its turn, and more than 

 one bud may be borne by either or both parent- or daughter- 

 cells. In very rapid growth the connection may persist between 

 the cells even during the formation of several generations of 



o o 



buds ; but this is unusual, and in cases where a number of cells. 

 remain apparently united together forming tree-like forms there 

 is often no real connection, the cells separating readily on agita- 

 tion. 



Endospores (Ascospores). Some yeasts in addition to the 

 method of reproduction by budding exhibit another mode known 



FIG. 97. Spores of Yeast (Ascospores). Three- and two-celled stage of spore for- 

 mation in S. cerevistce. 



as endogenous division or ascospore formation. Under certain 

 circumstances not yet entirely understood there are formed 

 within the yeast-cell two, three, or four rounded shining spores. 

 These become surrounded by thick walls and thus give rise 

 eventually to a group of daughter-cells within the original cellu- 

 lose sac. To the latter the term ascus (sac) has been applied, 

 and to its contained daughter-cells the term asco^ores. 



It is not yet allowed by all botanists that this terminology, which im- 

 plies a relationship of yeasts to the Ascomycetous fungi, is sound ; but it 

 is commonly used. 



Each ascospore is capable under favorable circumstances of 

 sprouting and starting a new series of generations of ordinary 

 yeast-cells. It should be particularly observed that the endo- 

 spores of yeast are reproductive bodies, and that the process of 

 their formation is one of multiplication not merely one of de- 

 fence or protection, as is the case with the so-called " spores ' 

 of bacteria described beyond (p. 194). 



