136 AGRICULTURAL BACTERIOLOGY. 



as shown by strict laboratory experiments. The results show 

 that Alinit consists of nearly a pure culture of a definite species 

 of microorganism which has been named B. ellcnbachiensis 

 (Fig. 1 8) and is closely allied to a common soil bacterium, B. 

 megatherium. This organism has the power of fixing free ni- 

 trogen under certain circumstances, and also of reducing nitrates 

 to nitrites under other conditions. It may thus have two dif- 

 ferent functions in the soil. 



But in spite of its theoretical utility the practical application of 

 Alinit to the soil for the purpose of increasing the yield of crops 

 has not been so universally satisfactory as to warrant its general 

 recommendation. Some experimenters have announced a de- 

 cided increase in yield, while others have found that the use of 

 Alinit has not resulted in any greater harvest than that ob- 

 tained from similar soil without the Alinit. On the whole the 

 positive results have been more numerous and more emphatic 

 than the negative, but have not been abundant enough as yet to 

 warrant any very definite conclusions. Whether it will be 

 possible by any similar means in the future to furnish the soil 

 with more valuable bacteria for the purpose of utilizing nitro- 

 gen is uncertain. With the evidence at present in our hands 

 it seems that the most promising method of preparing the soil 

 so that plants can obtain the largest amount of nitrogen, is not 

 by the addition of extra microorganisms, but rather by such 

 tilling and cultivation of the soil as will stimulate the growth 

 of the microorganisms present. The probability is that soil at 

 all times contains all kinds of nitric organisms in sufficient 

 quantity for all purposes. To produce nitrogen fixation the 

 proper conditions are needed and these can be obtained by the 

 cultivation and stimulation of the soil rather than by adding more 

 bacteria. 



BACTERIA AND LEGUMINOUS PLANTS. 



Nitrogen Fixation by Legumes. There is a second means 

 at the disposal of the fanner for increasing his nitrogen store, 



