THE QUEST OF NITROGEN 115 



was given the plants or added to the soil, either before 

 planting or during any stage of growth. 



These observers noticed a peculiarity the key of the 

 secret that others, also, doubtless, had observed, but 

 who failed to connect the same to the theory of plant 

 feeding and plant growth. The peculiarity which they 

 included in their studies was the characteristic growths or 

 nodules that persistently associated themselves with the 

 roots of every leguminous plant. 



A final proof of their theory was secured in this way : 

 They used sand that had been made sterile in every way : 

 all organic matter was destroyed, and, of course, every 

 kind of microscopic vegetation was killed no bacterium 

 of any kind was present in the soil. Some legume seeds 

 were now planted. Just as soon as the nitrogen of the 

 seed was exhausted, starvation manifested itself, and the 

 plants began their decline. At this point, a water extract 

 prepared from untreated soil just ordinary garden soil 

 was added, but only a small quantity was used. In a very 

 short time these starving plants began their improve- 

 ment : they recovered their wholesome, natural color, as- 

 sumed a vigorous, lusty growth, and reached full de- 

 velopment, with no suggestion from that time on that any 

 struggle or hardship had ever been a part of their exist- 

 ence. 



Of course, the succor which came at the opportune time 

 was none other than the friendly water solution that con- 

 tained the germs fitted by nature to gather nitrogen from 

 the wandering air in the soil, and to transfer it to the 

 starving plants. 



Experiments, variously planned and prosecuted, were 

 from now on in order. They served only to verify the 

 concluding theory. The secret, at last, was learned, the 

 mystery penetrated, and a new idea given the world. A 



