CHAPTER VI 

 METABOLISM OF COLORLESS PLANTS 



Nature, which governs the whole, will soon change all things 

 which thou seest, and out of their substance will make other 

 things and again other things from the substance of them, in 

 order that the world may be ever new. Marcus Aurelius. 



As representative of the diverse types of colorless plants 

 which, lacking chlorophyll or a functionally similar pigment, 

 are without the power of photosynthesis, we select the vast 

 group known as the BACTERIA. For reasons that will appeal- 

 later, it is not practical to focus attention on one particular 

 species of Bacteria, as we have just done in considering green 

 plants and animals. Instead we shall discuss in very general 

 terms the group as a whole, referring now and then to special 

 kinds of Bacteria to illustrate particular points. 



A. THE BACTERIA 



The wide distribution of the Protozoa is exceeded by the 

 Bacteria. Representatives are literally found everywhere: 

 floating with dust particles in the air; in salt and fresh water: 

 in the water of hot springs; frozen in ice; in the upper layers 

 of the soil; and in the bodies of plants and animals. Bacteria 

 have received a considerable notoriety under the names of 

 ' microbes ' and 'germs,' owing to the fact that certain types 

 get a living within the human body as parasites and bring 

 about disturbances, chiefly chemical, which we interpret as 

 disease. But aside from these forms, which are relatively 

 few in number, human life and life in general on the Earth 



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