28 

 BACTERIA CONTENT OF THE SUBSOIL 



An investigation was begun at the instigation of Hon. 

 George Coupland, Regent of the University of Nebraska, to 

 determine the lowest depth of subsoil in which micro-organisms 

 might be found. In order to facilitate the sampling it was 

 necessary that the subsoil, to the total depth projected, should 

 be exposed. Therefore a hole, which was approximately 

 four feet in diameter and twenty-one feet deep, was dug in an 

 alfalfa field on the farm of Mr. Coupland. Twenty-one 

 samples were taken at intervals of one foot along this per- 

 pendicular line. Four surface samples were also taken, east, 

 west, north and south of the excavation, at a distance of ten 

 feet. These samples represent two and four inch depths. 

 All samples were plated both on nutrient agar and on Ashby's 

 medium. Table number XI, shows no striking variation to 

 the sixth foot, except that the fourth level is abnormally high. 

 The oscillation thence to the thirteenth level is neither sur- 

 prising nor unprecedented, but the great preponderance on 

 the thirteenth level is unaccountable. No visible stratum of 

 impervious earth was observed. Alfalfa roots penetrated to 

 the lowest depth. While the number of bacteria on the thir- 

 teenth level was very great, yet, the flora was little diversified. 

 Cladothrix dichotoma being the principal representative. 

 Undoubted azotobacter were isolated from the third level. 

 Of the different species isolated from the above samples, 

 five fermented lactose bouillon with gas production. Fifty- 

 eight per cent reduced nitrates to nitrites. 



