YEAST AND BACTERIA 129 



Apparatus: The apparatus may be as shown in the 

 illustration on page 104, or a pickle bottle may be used in 

 the place of the flask. A box may be used in the place 

 of the ring- stand. 



Materials: Yeast cake, molasses. 



a. Dissolve the yeast cake in a small amount of 

 water and put it into the bottle which should be filled not 

 more than one-third full of lukewarm water. Add two 

 tablespoonfuls of molasses and shake well. Insert the 

 stopple and place the tube in test tube which should be 

 half full of limewater. In a few minutes bubbles will 

 begin to come from the molasses and pass into the lime- 

 water. How do you know that the gas is carbon diox- 

 ide? Compare this experiment with Experiment 41. 



While the first illustra- 

 tion of yeast shows the 

 growth of a single yeast 

 plant, it must be remem- 

 bered that in a mass of 

 yeast the plants will be 

 found in all stages of 

 growth. The illustration^ 

 shows what would be 

 seen if a small mass of 

 yeast were examined un- 

 der a very strong micro- 

 scope. See Section 78. 



50. Another Queer Kind of Plant The Bacteria. 



In several of our lessons we have read a little about 

 the plants called bacteria and have learned that they 

 grow fast in warm, damp places where the sun does not 



Cut supplied through United States Department of Agriculture. 



Elem. Sci. 9 



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Vii^X 



