37 The Physiology of Plants BOOK in 



seen, was marked by nitrification of ammonia. Wino- 

 gradsky's results were published in 1890. 



Further and quite conclusive proof was afforded by 

 Godlewski in 1895, when he showed that nitrification would 

 not go on and development of the organisms would not 

 occur in cultures containing magnesium carbonate when 

 no carbon dioxide was present in the air supplied to them. 



Winogradsky found that the process, which we may call 

 chemosynthesis, can take place as well in darkness as in 

 light, and is not therefore directly dependent upon a supply 

 of solar energy. His experiments showed him that the 

 energy employed in the construction is derived from the 

 oxidation of the ammonia. 



Winogradsky left our knowledge of the subject in- 

 complete, and no one has taken it further as yet. Nothing 

 has been ascertained as to the stages of the chemosynthesis. 

 He suggested that possibly urea is one of the products, 

 produced by polymerization of ammonium carbonate. 

 Hueppe, in 1887, and Loew, in 1891, suggested that the 

 initial stage may be the formation of formaldehyde from 

 the carbon dioxide and water. The problem still awaits 

 investigation. 



Another case of similar character was studied by Wino- 

 gradsky in 1887. This was the behaviour of the so-called 

 sulphur bacteria, species of Beggiatoa, which can flourish 

 in water containing sulphuretted hydrogen. He proved 

 that these microbes when supplied with such water flourish 

 luxuriantly and deposit aggregations of particles of sulphur 

 in their cells. These particles are subsequently removed, 

 or dissolved out by some process when the supply of 

 sulphuretted hydrogen fails. As in the case of the nitrify- 

 ing microbes, Beggiatoa contains no photosynthetic pig- 

 ment, but gets its energy by the process of oxidizing 

 inorganic substance in this case sulphur. It grows with 

 great freedom in water containing besides sulphuretted 



