MICRO-ORGANISMS 



first mistaken as -signs of the plants being 

 diseased. Further investigation proved 

 that they were caused by colonies of bac- 

 teria which had the invaluable property 

 of what is termed " fixing " the free nitro- 

 gen of the air. Nitrogen is a most im- 

 portant ingredient in all real foods, 

 whether meat or bread, but though three- 

 fifths of the air is composed of nitrogen, 

 none of this vast supply can be used for 

 food any more than the water of oceans 

 can be used for drink. Cereals like wheat 

 can get the nitrogen for their seeds only 

 in the small quantity and roundabout 

 ways afforded by decomposing animal 

 secretions or other decaying organic 

 matter. Hence the high price of manure 

 per load. 



Meantime bread-eaters are increasing at 



such a rate that according to Sir William 



Crookes, much too soon for comfort, there 



will not be manure enough, nor any other 



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