CHAPTER V 



FIXATION OF NITROGEN BY LEGUMINOUS PLANTS 



Beneficial effect of growing leguminous plants Liebig and the 

 chemical era A fundamental error corrected by Lawes and 

 Gilbert Their experiments on legumes Pasteur, Schloesing, 

 and Miintz's discovery Warrington's solution of the nitro- 

 gen problem for non -legumes Hellriegel and Wilfarth's 

 paper Their experiments on legumes Behaviour of the 

 plants explained Importance of bacteria Ward's inocula- 

 tion of legumes Beyerinck's Bacillus radicicola Nobbe's 

 culture Experiments in the United States and in England 

 Conclusions of the Board of Agriculture Work at King's 

 College Field experiments with nitrobacterin Successes 

 and failures Unfavourable conditions Disappointments 

 Nature of benefit to be expected The Bacillus radicicola 

 Mechanism of symbiosis Chemistry of the process 

 Effect of over-rich soils Balance between plant and bac- 

 teria A trade analogy Hopefulness of outlook. 



FROM the earliest days of agriculture practical men 

 have recognized the fact that the fertility of the soil 

 was increased by the growing in it of leguminous 

 crops. It is only within the memory of living man, 

 however, that it has been possible to state definitely 

 what actually occurs in connection with leguminous 

 plants. A convenient date from which to start 

 tracing out the stages through which the whole 

 problem relating to leguminous plants has been 

 carried is the year 1840. It was then that the 



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