ENTRY INTO THE BIOSPHERE 365 



The sulphides formed in the soil or in water can be again converted into 

 sulphates, either by a purely chemical action or by the action of various 

 bacteria, colourless sulphur bacteria, purple sulphur bacteria, etc. 



REFERENCES 



Hill, R. and Whiltingham, C. P. (1955). Photosynthesis. Methuen, London. 

 Lees, H. (1955). Biochemistry of Autotrophic Bacteria. Butterworth, London. 

 Bassham, J. A. and Calvin, M. (1957). The Path of Carbon in Photosynthesis 

 Prentice-Hall, Englewood Cliffs, N.J. 



