I IO SOILS 



2. That nitrogen is secured by plants through the ab- 

 sorption of soluble organic substances. 



3. That nitrogen is due wholly to the atmosphere : the 

 Liebig "mineral theory." 



4. That neither legumes nor cereals are able to "fix" the 

 nitrogen of the air. 



5. That leguminous plants get their nitrogen from the 

 atmosphere and others do not. 



6. That the soil, aided by microscopic vegetation, gath- 

 ers free nitrogen from the air. 



7. That bacteria in the root nodules are responsible for 

 the fixation of nitrogen and the transfer of it to the plant. 



The first theory: All elements came from the soil. 

 Until science was ready to devote itself, in a measure, at 

 least, to some practical problem, like a study of soils, 

 plants, or animals, progress could be slow only, and 

 theory of little value save in a most indirect way. Until 

 proof might be furnished, that should contain a grain of 

 fact or evidence as we consider such to-day, suggestions 

 would be of value, only, in that they occasionally worked 

 in sympathy with the governing law, unknown in what 

 manner or how, to the author, or to the disciple that fol- 

 lowed and practiced his philosophy. Evidence in these 

 cases were coincidences, only and of no further value. 



The second theory : Plants absorb soluble organic sub- 

 stances. The theory of absorption, in the light of knowl- 

 edge on these subjects, had some reasonableness about 

 it. This theory declared that only soluble organic sub- 

 stances were available as food for plants ; that as such 

 plants secured their food ; that organic substances fur- 

 nished not only the nitrogen but aH other substances as 

 well. And to a certain extent these ideas were correct. 

 The fault of this theory lay in its incompleteness. For 

 the mineral supply of food was quite overlooked: only 



