3-5 



THE YEAST CELL 



nucleus of a diploid cell in a spore wall. We have studied the via- 

 bility of the spores produced by our, apparently illegitimate, R- 

 strain culture in some detail. The 1-spored asci germinate directly 

 to produce diploid cells while the spores from asci containing more 

 than 1 spore are either non-viable or germinate to produce the char- 

 acteristic small haploid cells. The viable colonies obtained from 

 1-, 2-, 3-, and 4-spored asci of the R-strain are shown in the fol- 

 lowing tabulation: 



Type of Ascus Number Tested 



1-spored 

 2-spored 

 3-spored 

 4-spored 



16 



47 



4 



3 



Viable Colonies 



10 

 2 

 1 

 



Two-spored asci are generally more abundant than either 1-, 

 3-, or 4-spored asci. In fact, on some media, notably on potato 

 slants, 2-spored asci are produced almost exclusively. Cultures 

 which would normally produce a considerable number of 4-spored 



ASCI OF CROSSBRED 



ISOLATED WHOLE 

 4-SPORED ASCUS 



HANGING 

 DROP 



NORMAL COPULATION 

 GYPSUM 



COLONIES 



ON AGAR 



CULTURE ON GYPSUM 



A,B,C,D -SINGLE SPORES 

 DISSECTED FROM A 

 "4-SPORED ASCUS 



LARGE HAPLOID COLONIES, DELAYED COP 

 I I I i 



NON 



-VIABLE, 2-SPORED ASCI 



o 



o 



O QO O 



UNIFORM 



VARIABLE 



Fig. 3-1 Diagram Showing the Differences between Cultures 

 Originating from Intact 4-spored Asci and from Single Ascospores, 



