CONDITIONS FOR THE GROWTH OF BACTERIA 119 



little upright fruiting bodies. These fruiting bodies bear 

 tiny little seedlike structures, called spores, which are 

 blown around in the air, and grow under favorable condi- 

 tions. What are these conditions? Refer to your two 

 pieces of bread. Warmth and moisture are necessary for 

 the growth of all tiny organisms. Molds do considerable 

 damage, although 

 they do not render 

 foods completely un- 

 fit to eat. You all 

 remember scraping 

 the layer of mold 

 from cheese, before 

 using it. As a mat- 

 ter of fact, certain 

 cheeses get their 

 flavor from the 

 molds that grow in 

 them. Molds also 

 attack other organic 

 materials besides 

 foods. They grow 

 on shoes, leather, paper, or even moist wood. At least one 

 troublesome skin disease, called ring worm, is due to the 

 growth of molds in the skin. 



Conditions favorable for the growth of bacteria. By far 

 the most important enemies of pure foods are bacteria, which 

 cause food to decay. We can show the factors which in- 

 fluence the growth of bacteria by the following experiment : 



Experiment. What conditions are favorable and what unfavorable to the 



growth of bacteria ? 

 Materials: Beans. Test tubes. 



Three different types of mold plant. Notice the fruit- 

 ing bodies, containing spores, i. Cheese mold. 

 2. Corn smut. 3. Bread mold. 



