A MANUAL OF BOTANY 119 



/). Why are diseases of the nose, throat, and lungs so 

 common ? 



6. What agents kill bacteria or hinder their develoi^- 

 meiit ? 



7. Why is country air said to be more pure than that of 

 a large city? 



8. What would be the condition of things were there no 

 bacteria ? 



9. How may bacteria gain entrance to the human body? 

 10. What are "disinfectants," "antiseptics," "germi- 

 cides," "food preservatives," and "fungicides"? 



Typk .S. Common Black Mold of Bread ^ 



Home experiments. Take a small piece of bread which is 

 stale, moisten, rub on the floor, and place in a saucer. Over 

 all place an inverted tumbler, and set in a warm place. 

 Watch from day to day, and notice the first appearance of the 

 white " fuzzy " growth, and its further ^ development until 

 the whole has turned dark. Where did the mold come 

 from, and what, from your experiment, seemed to be the con- 

 ditions requisite for its growth ? Try the experiment again 

 without wetting the bread; also again, by keeping in a cold 

 spot. Wliy would no mold grow on a rock treated in the 

 same manner? As the bit of bread increases in age observe 

 the increasing discoloration by various colored patches ; also 

 the increasing offensive odor. These patches are probably 

 caused by bacteria (germs, microbes) and the bread is de- 

 caying, or decomposing. Which comes first, the bacteria or 

 the decay? 



Vary your experiment by using potatoes, raw or cooked, 

 banana skins, fruits, pieces of meat, chips of wood, or other 

 matter of organic (produced by living things) nature. Ob- 



1 Mucor, Rhizopos. 



