COMPETITIVE INTERRELATIONSHIPS 45 



known to be an active cellulose-decomposing organism, did not attack 

 at all the cellulose of alfalfa and decomposed the hemicelluloses only to 

 a limited extent j however, the organism utilized the proteins rapidly, 

 as illustrated by the amount of ammonia liberated. Rhizofus^ a non- 

 cellulose-decomposing fungus, attacked largely the hemicelluloses in 

 the alfalfa and some of the protein j a small reduction in cellulose was 

 recorded, probably because of an analytical error. When Trichoderma 

 was combined with Rhizofus, the former attacked readily both the cel- 

 lulose and the hemicelluloses. The same effect upon the activity of 

 Trichoderma was exerted by other noncellulose-decomposing organ- 

 isms, such as the fungus Cunnmghamella and the bacterium Ps. fuores- 

 cens. On the other hand, when Trichoderma was combined with a cellu- 

 lose-decomposing Streftomyces, there was considerable reduction in the 

 decomposition of the total plant material as well as of the cellulose and 

 hemicelluloses. These results further emphasize the fact that two or- 

 ganisms may either supplement and stimulate each other or exert an- 

 tagonistic effects. The total soil population is far more active than any 

 of the simple combinations of microorganisms. 



COMPETITIVE INTERRELATIONSHIPS 



The following competitive relations among the microscopic forms of 

 life inhabiting the sea have been recognized (i8) : 



Competition among chlorophyol-bearing diatoms for the available nutri- 

 ent elements in the water 



Competition among the copepods for the available particulate food mate- 

 rials, notably the diatoms 



Competition between individuals belonging to one species and individuals 

 belonging to another 



Competition between young, growing, and reproducing cells and older, 

 respiring cells 



Food competition and space competition 



Competition between transitory and permanent populations 



Competition between sedentary or sessile organisms and free-moving forms 



This list has been enlarged (924) to include other factors that are par- 

 ticularly prominent in nonaquatic environments : 



