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are intricate relationships in nature which operate together to 



support, and to also to control the undue increase of all forms of 



life. These forces of nature are so balanced in the competitiire 



» 

 struggle for existence that but one reparoduction unit commonly 



succeeds another. Were any species of terrestrial plant or animal 



allowed to reproduce and multiply unchecked, it would in a few 



years cover the earth and crowd out all other forms of life. 



To appreciate this lELance in nature, let us consider the con- 

 ditions in a primeval forest before it has been affected by the 

 inroads of civilization and settlement. For our purpose it is 

 necessary only to consider the important forms of life in the for- 

 est community, and to treat them briefly in groups, proceeding 

 from the lower to the higher forms in our classification, and not- 

 ing the more important influences which they exert. 



The bacteria and fmngi in the forest cause decay . 

 and decomposition of organic matter, and convert it into the nour- 

 ishment necessary for the life of higher vegetation, were it not 

 for these agents of decay, all the chemical elements capable of 



sustaining life would have been used up long ago, and life on this 



( 1 i* 

 earth would have ceased.* ' On the other hand, these fonns also 



cause some well known diseases of plants and animals, which tend' 



to hold their nximbers in check. 



The higher plants use and store the nourishment provided by 



the bacteria and fungi and convert it into plant tissue which 



directly or indirectly provides food necessary for the existence of 



all animal> life.* 2' 



* References to bibliography are numbered consecutively thruout the 

 text 



