THE BIOLOGICAL RELATION BETWEEN BACTERIA AND THE MORE 

 HIGHLY ORGANIZED FLORA OF RUNNING STREAMS. 



By D. H. Bergey, M. D. 

 First Assistant, laboratory of Hygiene, University of Pennsylvania. 



[Read before the Biological Club, March 7, 1898.] 



All cryptogamic plants may be divided into two great 

 classes with reference to the presence or absence of chloro- 

 phyl within the plant cells. When we come to study the 

 life history of these two groups of organisms we find that 

 their biological functions are closely related to the fact 

 whether they contain chlorophyl or not. 



In many respects the biological functions of the two 

 groups of organisms are entirely different from each other. 

 Those cryptogamic plants which contain chlorophyl in 

 their cells possess biological functions not markedly dis- 

 similar in character to those of the phanerogamic plants. 

 Those of the cryptogamic plants which are without chlo- 

 rophyl have biological functions which are entirely differ- 

 ent from those of the phanerogamic plants. 



As the basis of our study of the relation between the 

 biological functions of bacteria and the more highly organ- 

 ized flora of running streams we shall take into considera- 

 tion the nature of their food supply. The food supply of 

 the more highly organized flora does not differ in any 

 essential respect from that of the phanerogamic plants. 

 They subsist on the various mineral matters contained in 

 the soil and water and upon the constituents of the atmos- 

 phere. For the healthy action of all their body cells they 

 require, in addition, the presence of sunlight. Their chlo- 

 rophyl-bearing cells are dependent upon the influence of 

 sunlight for the power of building up the most complex 

 organic compounds and elaborating them into the various 



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