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SCIENCE 



[N. S. Vol. XXXVI. No. 932 



be misunderstood as minimizing the impor- 

 tance of a real knowledge of the activities 

 of the micro-flora and fauna of the earth. 

 Rather would I hope to emphasize this 

 aspect of the question, which I suppose is 

 what was expected when the subject was 

 assigned to me. It is quite as important, 

 however, to point out the unsatisfactory- 

 state of the investigations at present and 

 the futility of generalizing from a few 

 known facts, acquired by disregarding a 

 vast number of unknown, but nevertheless 

 real, factors. 



Fischer, you will remember, after a more 

 or less critical review of the situation, 

 came to the conclusion that we do not now 

 possess a method of bacteriological exam- 

 ination of soils, which is of the least prac- 

 tical value. While not subscribing to this 

 view, it must be confessed that a study of 

 the literature on the subject indicates that 

 much of fundamental importance remains 

 to be done before we can hope that an 

 investigation of the microorganisms of the 

 soil will result in really solving some of the 

 perplexing problems of fertility now con- 

 fronting us. Even the nomenclature of 

 the subject is so indefinite at the present 

 time, that within the past year we have 

 had conflicting uses of such familiar terms 

 as "nitrification" and "nitrogen fixing" 

 and there certainly is need for some such 

 unification and strict definition of terms 

 as that suggested by Lipman. 



An enumeration of all the methods now 

 in vogue for the bacteriological examina- 

 tion of the soil would show that the tech- 

 nical side of the subject is in much the 

 same condition that water bacteriology was 

 fifteen years ago, and until there is more 

 uniformity in methods employed, by which 

 comparative tests can be made, we shall not 

 gain much from the results of the steadily 

 increasing number of workers in this field. 

 It is true that new points of view are occa- 



sionally presented and a distinct step in 

 advance has been the emphasis recently 

 placed upon the study of the organism, as 

 far as possible, in its natural environ- 

 ments, rather than in artificial solutions. 

 The work of Vogel, Stevens and others, has 

 done something to make possible an agree- 

 ment in parallel laboratory and field ex- 

 periments; but, after all, progress in this 

 line has been chiefly through pointing out 

 the errors of others and has not resulted, 

 as yet, in the formulation of a standard. 

 We are much farther along in knowing 

 what not to do, but like the Sherman law, 

 the situation calls for some affirmative 

 legislation. 



There is also considerable evidence that 

 we have been so obsessed by the pure cul- 

 ture idea, that conclusions drawn from 

 experiments performed under such condi- 

 tions are entirely unwarranted. If it is 

 true that mixed cultures of Azotobacter 

 cJiroococcum and Pseudomonas radicicola 

 will flx almost twice as much nitrogen as 

 either alone, to say nothing of the neces- 

 sary interaction between various groups in 

 making available green manures, phos- 

 phoric acid, lime nitrogen, etc., it is very 

 evident that conclusions drawn from the 

 study of a single organism can not be ap- 

 plied to the conditions actually existing in 

 the soil. We might as well assume that a 

 superior being, dipping down into our at- 

 mosphere and selecting a single individual, 

 would be able to arrive at the various func- 

 tions and activities of man on the face of 

 the globe, by observing his behavior under 

 such artificial conditions as it would be 

 possible to maintain in a heavenly labora- 

 tory. It is neither necessary, nor ad- 

 visable, of course, that we abandon the 

 pure culture method. But we should 

 recognize the limitations of our present 

 technique and cease to generalize from 

 such inadequate data. 



