1912] Llpinaii : Barieria hi Soils of Arid Eegionn 19 



never gave evidence of vigorous bacteria, nor did alkali soils 

 or soils devoid of humus. 



Secondh^, the writer desires to anticipate criticism on the 

 method used in culturing the organisms of the various soil 

 samples, viz., a modified Remy solution method. No one is more 

 ready than I am to admit the just criticism made of the solu- 

 tion-culture methods in soil bacteriology. Indeed I believe that 

 •I was one of the first to put into practice on a large scale the 

 direct soil-culture method in the laboratory. But when problems 

 of the nature involved in these investigations must be attacked, 

 regard nnist ])e had for the chances of contamination in the 

 method employed, and for the feasibility of obtaining, uncon- 

 taminated, large volumes of soil for use in these experiments. 

 When these were considered from all points of view, only one 

 feasible and reliable method of culturing the soils seemed avail- 

 able and that was the solution method. The difficulties, prac- 

 tically insurmountable, which must arise with any other method, 

 when such work is carried out on a large scale as it must of 

 necessity be, can ])e fully appreciated by those who have ever 

 attempted it. The gratifying results obtained in this work, how- 

 ever, seem to me a further justification of the methods em- 

 ployed. 



It seems of particular moment now, to call the attention of 

 soil bacteriologists in particular, and soil scientists in general, 

 to the important field explored in these investigations and the 

 striking results obtained therefrom, not only because it repre- 

 sents a new field of research, but because it emphasizes more 

 strongly than ever the radical differences which obtain between 

 soils of the humid and arid regions. It also helps to explain 

 the extraordinary appearance of our subsoils (if subsoils they be) 

 and the marvellous root developments of which plants under our 

 climatic conditions are capable. While these studies have not yet 

 departed from the realms of the preliminary, they are replete 

 with facts which are already of considerable practical and scien- 

 tific significance and which are doubtless destined to become 

 more so as time progresses. As a part especially of a comprehen- 

 sive soil study they are invested with unusual importance and 

 may help tO solve problems now perplexing and difficult to study. 



