PLANTS IN THEIR RELATION TO HUMAN WELFARE 149 



158. Suggestions for laboratory work on yeast. No. 62. 

 Students should examine the appearance of yeast cells under the 

 low and high powers of the compound microscope. If time permits, 

 the demonstration of carbon dioxid production and of distillation 

 of alcohol might well be made. (See Peabody's " Laboratory Exer- 

 cises," pp. 94-99, Henry Holt & Co., New York City.) 



C. Bread Mold (Optional) 



169. Structure of bread mold. If pieces of bread or cake be 

 moistened, and placed in a dish, and covered with a bell- jar in the 



FIG. 75. Bread mold, showing nutritive hyphae (A) ; reproductive hyphae 

 CB) ; and spore cases (C). (Osterhout.) 



dark, in a few days grayish patches will appear in places on the 

 surface of the bread. This growth is due to the activity of one 

 of the fungi, known as a mold, and will probably be the kind 

 called bread mold. No care is required to produce the plant in 

 quantities ; on the contrary, as common experience shows, some 

 pains must be taken by the housekeeper to prevent it from spoil- 

 ing food. 



When the bread mold is examined with a hand lens, it is seen to 



