Highly Organized Flora of Running Streams. 7 



ordinarily satisfy their requirements for carbon and nitrogen 

 by taking these elements from CO 2 and NH 3 , or even HNO 8 , 

 out of substances in their environment, and converting 

 them into complex carbonaceous and nitrogenous matter 

 with the aid of the chlorophyl. It is possible for these 

 plants to take their nourishment out of water containing 

 the necessary mineral substances, and out of air containing 

 CO 2 and NH 3 and assimilate the carbon and nitrogen de- 

 rived from these sources. They also possess, to a limited 

 extent, the power of breaking up organic matter and 

 derive their C and N directly from such matter. The 

 bacteria, however, through the absence of chlorophyl, are 

 incapable of existing in this manner, but require previously- 

 prepared organic substances to meet the needs of their 

 bodies, and to form new substance. Therefore, they cannot 

 exist in pure water containing only mineral matter. They 

 vegetate on dead organic matter, rich in carbon and nitro- 

 gen, and likewise on dead plants and animal organisms, or 

 they live as parasites drawing the organic matter necessary 

 for their life and growth from their vegetable and animal 

 hosts. 



From this one may form an idea as to the significance 

 of the bacteria in nature. In order to provide continu- 

 ously the simple nourishment necessary for the chlorophyl- 

 bearing vegetation, it is essential to have a constant reduc- 

 tion and solution of this form of vegetable substances back 

 into simple chemical combinations. The entire yearly 

 vegetation which has formed and died must be so changed 

 in a relatively short time that the complicated vegetable 

 substances, the albumen, carbo-hydrates and cellulose are 

 again converted into water, CO 2 and NH S . Only under 

 such conditions is the continuous regeneration of the 

 higher vegetation possible. 



A part of this work of reconstruction falls upon animal 

 organisms, the animal cells breaking up the vegetable 

 matter taken up, and delivering it over for oxidation. 



