136 



MYCOLOGY 



in young cells and these ultimately fuse to form a single vacuole which 

 occurs in the cells during the earher and the later fermentation. The 

 process of budding is associated with the stretching of a network of nu- 

 clear granules and its final constriction in the neck between the mother 

 and the daughter cell. The nucleolus moves to the constriction where 

 it becomes dumbbell- 

 shaped, one half press- 

 ing into the daughter 

 cell (Figs. 44 and 45). 

 There are no stages of 

 karyokinesis dis- 

 played, but by the sim- w^ f 1,«k W /<^ 

 pie process described ^^ -"^ ^^^ ^ ^^ 

 above the daughter 

 cell receives approxi- 

 mately one-half of the 

 nuclear substance of 



r^ 



^ 



y^^r. 



Fig. 45. Fig. 46. 



Fig. 45. — Young yeast cells, Saccharomyces ellipsoideus, with nuclei and division 

 of nuclei. (After Marshall, Microbiology, Second edition, p. 64.) 



Fig. 46. — Yeast, Saccharomyces cerevisice, the variety known as brewers' bottom 

 yeast; a, spore formation; h, elongated cells. {After Schneider, Pharmaceutical Bac- 

 teriology, p. 144.) 



the mother cell. In spore formation, the chromation which is scattered 

 through the cytoplasm is absorbed more or less completely into the 

 nucleolus which elongates and divides by a constriction in its middle 

 part. Subsequent divisions result in the formation of four nucleoli 

 around which protoplasm collects and thin membranes which become 

 the walls of the ascospores which remain at first small, but later increase 

 in size (Fig. 46). The formation of spores can be secured by taking 



