ROLE OF BACTERIA IN NATURE 35 



the form of corn, wheat, or alfalfa every pound of commercial nitro- 

 gen that has been applied to the soil, which, on the face of it, is an 

 utter impossibility. So we have to look to other means of getting 

 nitrogen for our growing crop, and here again bacteria come to our 

 rescue. 



I There are seventy-five million pounds of atmospheric nitrogen 

 resting upon every acre of land. None of the higher plants, however, 

 have the power of taking this directly out of the air. One family 

 of plants, the Leguminosse, in which are included peas, beans, alfalfa, 

 clover, and many others, if properly infected by bacteria have the 

 power of using this atmospheric nitrogen. Under this condition 

 and with these plants nitrogen no longer remains the limiting ele- 

 ment of crop production. For these microscopic organisms which 

 live within small nodules upon the alfalfa are master chemists. 

 Within their tiny laboratory they can bring about changes which 

 man can imitate but imperfectly with costly machinery and under 

 the action of powerful electric currents. In some of the experiments 

 carried on at the Illinois Experiment Station these minute organisms 

 were found to be able to increase the value of the first cutting of 

 alfalfa hay $27.80 an acre, if the nitrogen in the alfalfa be counted 

 only at the same price as we would have to pay on the market for 

 an equivalent quantity of nitrogen in the form of a commercial 

 fertilizer! If these crops be plowed under the fertility of the soil 

 would be increased to just that extent. One writer has said of them: 

 "They not only work for nothing and board themselves, but they 

 pay for the privilege." This is strictly true, for all they require is a 

 plant on which to grow and a well-aerated moist soil containing 

 limestone. /They cannot work in an acid soil. 



There is another class of nitrogen-gathering organisms within the 

 soil which differs from the above in that they live free in the soil 

 and gather nitrogen. Under ideal conditions they may gather 

 appreciable quantities. 



It is quite possible that much of the benefit derived from the 

 summer fallowing of land is due to the growth within the soil of this 

 class of organism which stores up nitrogen for future generations 

 of plants. It has been found that they are more active and found 

 in greater numbers in such a soil. All the work that the farmer puts 

 upon the soil to render it more porous reacts beneficially upon these 

 organisms, because they not only love atmospheric nitrogen and 

 oxygen, but must have them. These elements are absolutely essen- 

 tial to their life activities and they must be obtained from within 

 the soil since the minute organisms cannot live upon the surface for 

 the direct rays of the sun kills them in a short time. 



But these are only a few of the many that help the farmer. They 

 are at work in his silo rendering the feed more palatable and nutri- 

 tious for his cattle. They are working in his milk and cream, and 



