256 



CRYPTOGAMS 



rice, etc. Try some of these which have been sweetened 

 and others plain. What may be inferred from these experi- 

 ments ? 



From the foregoing Experiments, answer the following 

 questions : 



Under what conditions does yeast develop? What 

 effect has heat on the growth of the yeast plants? How 

 does cold affect their growth? What is given off by these 

 plants? On what substance does yeast feed? How may 

 fermentation be stopped ? How may it be hindered ? What 

 gas is produced by yeast? How do you account for the 

 frothing of liquids containing yeast? What causes bread 

 to rise? Will fermentation go on forever? If not, why 

 not? Reasons for your answer. How long will fermenta- 

 tion continue? 



219. YEAST (optional) 



Object. To observe the form of yeast plants and their 

 manner of reproduction. 



Method. Mount a drop of liquid yeast or any substance 

 in which yeast is growing and cover it with a cover glass. 

 Examine it first with a low power and then with a higher 



power objective. Note the oval 

 cells of yeast. Are all of equal 

 size ? Find cells which are joined. 

 Look for cells producing smaller 

 cells (buds). Sometimes several 

 cells can be distinguished, forming 

 chains or colonies. What is the 

 color of these plants? Can they 

 manufacture starch ? Give reasons 

 FIG. us. Yeast plants. for your answer. 



