104 



L. T. SHARP 



and Blanck observed a notable and persistent depression of 

 nitrification due to drjdng of the soil. 



From the foregoing review of the literature concerning desic- 

 cation it would appear that organisms persist longer in the soil 

 than when exposed to drying conditions on some other media. 

 That bacterial action is qualitatively and quantitatively different 

 in soils from what it is in artificial media is the logical reason for 

 adopting soils as the proper media for the determination of the 

 bacterial efficiency of the soil flora; similarly it is not unreason- 

 able to expect that soils in drying, presenting peculiar physical 

 and chemical conditions, exert a totally different destructive 

 force on the organisms from that concerned when they are dried 

 on artificial media. The ammonification flora, embracing numer- 

 ous species of organisms exhibiting a wide range of physiological 

 activity, seems to possess, as a group, a greater resisting power 

 toward drying than either the Azotohacter species, B. radicicola, 

 or Nitrosomonas and Nitrobacter. 



Having some soil samples^" which had been tightly stoppered 

 for the last twenty-five to thirty-three years placed at my dis- 

 posal, it appeared of great interest to investigate the bacteriologi- 

 cal flora existent in them. With this end in view the present 

 work was planned and executed to determine the remaining 

 potency of the micro-flora still present. This phase of soil biol- 

 ogy, — that of the resistance of organisms to drying of the soil, — • 

 offers attractive research problems, because of its practical appli- 

 cation and scientific interest. 



EXPERIMENTATION 



It was planned to study the soil from four aspects, the number 

 of organisms present, and their physiological characteristics as 

 manifested by their ammonification, nitrification, and nitrogen 

 fixation powers. However, before proceeding to the experi- 

 mental details, it is essential for possible correlation between 



2° The soils used in these experiments were chosen from the collection of Dr. 

 E. W. Hilgard, who kindly consented to their use in the furtherance of the inves- 

 tigation. 



