CHAPTER XV. 

 UNICELLULAR PLANTS (Continued). 



B. Yeast. 

 (Saccharomyces.) 



UNDER the general name of yeast are included some of the 

 simplest forms of vegetal life. Some yeasts are "wild," liv- 

 ing upon fermenting fruits or in fruit juices, and commonly 



FIG. 93. Yeast-cells. Brewer's (top) yeast actively vegetating. The large internal 

 vacuolcs and the small fat-drops are shown, as are also buds, in various stages of 

 development, and the cell-wall. Nuclei not visible. (Highly magnified.) 



occurring in the air; others are "domesticated," or cultivated, 

 such as those regularly employed in brew-ing and in baking. 



If a bit of "yeast-cake " (either "compressed "or " dried" 

 yeast) is mixed with water, a milky fluid is obtained which 

 closely resembles the so-called baker's or brewer's yeast. 



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