BACTERIA. 157 



one of the prime factors in making continued life 

 on the globe possible. 



HOW DECAY INCREASES FERTILITY. 



It must not be forgotten that bacteria cause 

 decay of small creatures as well as of large ones, 

 and that the fertility of the soil is due largely to 

 the decay of many minute plants and animals. 

 Untold millions of insects, and other small animals, 

 among plants and in the ground, die annually. 

 Their bodies are covered with decomposition 

 germs, too, and they pass through the same stages 

 of decay and change as the higher forms. 



There are few better ways of increasing the 

 fertility of a piece of land than to let it "rest"; that 

 is, to cease cultivation and let it grow up in weeds. 

 The increased fertility comes from the rapid decay 

 of the great numbers of small plants and animals. 

 For this reason it is always better to let a field 

 grow up in weeds than to keep the surface clean. 

 The weeds naturally afford forage and breeding 

 places for insects and other small animals whose 

 life is very short. They all die and are returned 

 to the soil at the end of the season. 



Bacteria live in the soil as well as on its surface. 

 They help to decompose organic matter mixed 

 with the soil. They are very numerous near the 

 surface, and decrease downward. At a depth of 

 five or six feet few, or none, are found. 



Often organic matter in some soils will not 



