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 likely to become cloudy 



E 



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

 its parts ; a, vacuole; b, nucleus; c, d, reserve food. B, 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 full 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 -j-^-j 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 



