Febbtjabt 10, 1911] 



SCIENCE 



231 



land region, give fine yields, often the crop 

 fails to give both quantity and quality even 

 under our best planned systems of rotation 

 and of soil fertilization. 



4. Experiments in soil sterilization applied 

 to such old and supposedly deteriorated soils 

 have uniformly given quite marked improve- 

 ment in results. The results have been so 

 uniformly good, whether done by steam or by 

 chemical methods, that one or other practise 

 has become general with the glass house gar- 

 deners and seedling plant producers. They 

 seem, long ago, to have realized what steriliza- 

 tion of soil has done for them, but experi- 

 menters upon field crops still look for explana- 

 tion for such improvements. 



5. Two very interesting explanations of such 

 effects of sterilization, both based upon care- 

 fully planned and executed experiments, have 

 lately been attempted; and, as my experiments 

 cover essentially the same fields of effort, and, 

 when published, will show almost exactly the 

 same results but quite different conclusions, 

 I may be pardoned, at this time, for outlining 

 these three sets of experiments and the results, 

 with some slight comment upon the conclu- 

 sions : 



Mr. A. D. Hall, of Eothamsted, England, in 

 Science, September 16, 1910, reports upon 

 experiments conducted at the Eothamsted 

 farm. 



Speaking of wheat, he says: 



Approximately the crop becomes double if the 

 soil has been first heated to a temperature of 

 70° to 100°, for two hours, while treatment for 

 forty-eight hours with the vapor of toluene, 

 chloroform, etc., followed by a complete volatiliza- 

 tion of the antiseptic, brings about an increase of 

 thirty per cent., or so. Moreover, when the ma- 

 terial so grown is analyzed, the plants are found 

 to have taken very much larger quantities of 

 nitrogen and other plant foods from the treated 

 soil; hence, the increase of growth must be due 

 to larger nutriment and not to mere stimulus. 



The explanation, however, remained in doubt 

 until it has been recently called up by Drs. 

 Russell and Hutchinson, working in the Eoth- 

 amsted Laboratory. In the first place, they 

 found the soil, which had been put through the 

 treatment, was chemically characterized by an 

 exceptional accumulation of ammonia to an extent 



that would account for the increased fertility. 

 At the same time it was found that the treat- 

 ment did not efifeet complete sterilization. . . . 



The question now remaining was, what had 

 given this tremendous stimulus to the multiplica- 

 tion of the ammonia-making bacteria? By vari- 

 ous steps, which need not here be enumerated, the 

 two investigators reached the conclusion that the 

 cause was not to be sought in any stimulus sup- 

 plied by the heating process, but that the normal 

 soil contained some negative factor which limited 

 the multiplication of the bacteria therein. 



Examinations along these lines then showed 

 that all soils contain unsuspected groups of large 

 organisms, of the protozoa class, which feed upon 

 living bacteria. These are killed off by heating, 

 or treatment by antiseptics, and on their removal, 

 the bacteria, which partially escape the treat- 

 ment, are now relieved from attack. . . . 



Curiously enough, one of the most striking of 

 the larger organisms is amoeba. 



The authors, Messrs. Eussell and Hutchin- 

 son, thus attempt to account for the greater 

 wheat crop production of soil sterilization 

 both through chemicals and through steaming, 

 by a reverse application of the Metchnikoff 

 theory. It would be unwise of me, not know- 

 ing all of their data or having access to the 

 soil or the seed which they used, to enter a 

 criticism, but from my own observations and 

 work, I can not agree to any of the conclu- 

 sions which are drawn in these paragraphs. 

 So far as Mr. Hall has made plain in Science, 

 they can only be matters of inference, and 

 many conditions could enter, which would 

 vitiate the necessity of assuming the detri- 

 mental role for the amoeba. For example, the 

 authors do not explain why their sterilization 

 did not sterilize, and what happened when 

 they did really sterilize the soil. In order to 

 clarify the theory as proposed by Dr. Hall, it 

 would seem necessary to try real sterilization, 

 both upon the amoeba and the supposedly bene- 

 ficial bacteria. 



It is quite possible- that the production of 

 ammonia in soils by bacteria is a beneficial 

 process, but I can not say wherein this theory 

 would rest, if one should assume the presence 

 of plenty of ammonia and plenty of ordinary 

 nitrates in the soil. In such case, if the soil 

 still failed to produce wheat, and proper ster- 



