PRESIDENTIAL ADDRESS. 49 



not return to their original proportion for at least two 

 years. The denitrifying bacteria, originally fairly numer- 

 ous, were almost completely destroyed, and did not appear 

 to any extent for two years. The pectin-fermenters which 

 were originally as numerous as the denitriflerswere reduced. 



The nitrogen-gathering nodule-former of the Leguminosae 

 is not destroyed by some disinfectants, such as ether and 

 hydrogen peroxide; 1 on the contrary, its growth is favour- 

 ably influenced. The ammonia-producing bacteria are 

 increased and the putrefactive processes are less intensive. 

 The nitrifying organisms are apparently temporarily checked 

 but subsequently develop with considerable intensity. 



The hindrance which the nitrification receives is an 

 advantage to the soil and crop in a moist climate, for, when 

 the disinfectant is applied in the autumn, nitrates are not 

 formed, and there is consequently no loss of nitrates by the 

 winter rains. In spring, when nitrification becomes active, 

 the nitrates are available for the plant -at a time when 

 they are of most value. The destruction of the denitrifiers 

 also helps to conserve the soluble nitrogen. 



The alteration in the bacterial flora and the nature of 

 the subsequent fermentation of the soil constituents appear 

 to be the reason for the enhanced fertility. If the soluble 

 soil constituents are increased in amount, they can be 

 present only as traces, for several investigators have failed 

 to detect any change either in the total soluble matter 1 or 

 in the soluble minerals. 2 There is an undoubted production 

 of ammonia 3 which is formed instantaneously. 4 



The inability to detect traces of soluble matter led several 

 authors to agree with Koch's hypothesis that the increased 



1 Nobbe and Eichter, Cent. Bakt. 2jte, 14, 234. 



2 Moritz and Scherpe, Ibid., 13, 573. 



3 Heinze, Ibid., 16, 329. 



4 Eussell and Hutchinson, Journ. Agr. Sci., 3. 111. 



D— May 3,1916. 



