CHAPTER IV 



YEASTS 



49. A Yeast Culture. — If a portion of a cake of com- 

 pressed yeast or of dried yeast is put into a solution of mo- 

 lasses and the mixture is left in a warm place, in the course 

 of twenty-four hours the liquid is Hkely to become cloudy 



E 



Fig. 13. — A yeast. A, a single cell, killed and stained so as to show 

 its parts; o, vacuole; J, nucleus; t, (i, reserve food. £, the division of the 

 cell by budding. C, D, chains or colonies, formed by the remaining to- 

 gether of the daughter cells after division. E, spores inside the wall of the 

 mother cell. 



and ftdl of small bubbles that rise slowly to the surface. 

 Examining a drop of the liquid, we shall find that it contains 

 great numbers of rounded cells, some single and others in 

 chains of two, three, or more. These cells are yeast plants. 

 A yeast cell (Fig. 13, A) is larger than the bacillus that we 

 have studied (it is about -g-jnnr inch in diameter), but re- 

 sembles the bacillus in being colorless. It is either globular 

 or, more commonly, a little longer in one direction. It is 

 surrounded by a wall. 



33 



