50 FOUNDATIONS OF BIOLOGY 



Bacteria and other colorless plants. Such is the reciprocal 

 nature of the nutritive processes of living organisms. 



It is hardly necessary to state that the chemical changes 

 produced by the Bacteria are either the direct results of, or 

 are incidental to, the process of nutrition in these organisms. 

 Therefore the material taken as food by certain groups is 

 relatively complex, for example, by those which bring about 

 the early putrefactive changes in proteins; while that em- 

 ployed by others is very simple since they find adequate 

 chemical combinations less complex than those needed by 

 green plants. Indeed, it is now known that one group of 

 Bacteria is able to utilize carbon dioxide and water just as 

 do green plants. But instead of obtaining energy for the 

 synthesis from sunlight, these Bacteria derive it from chemi- 

 cal energy liberated by the oxidation of substances in their 

 environment. This process is referred to as CHEMOSYN- 

 THESIS, in contrast with photosynthesis, and although it is 

 apparently restricted to a relatively small group of organ- 

 isms, may well represent the most primitive method of 

 nutrition from which all the others have been derived in the 

 evolution of life. 



C. THE HAY INFUSION MICROCOSM 



The importance of the complex nutritional interdependence 

 of organisms in general and the cosmical function of green 

 plants the link they supply in the circulation of the ele- 

 ments in nature may be emphasized and summarized by 

 a brief description of a 'hay infusion. 1 



Probably nowhere is the 'web of life' more conveniently 

 or convincingly exhibited than in the kaleidoscopic sequence 

 of events physical, chemical, and biological which are 

 initiated when a few wisps of hay are added to a beaker of 

 water. Apparently the chief components of a hay infusion 



