50 R. GREIG-SMITH. 



growth of the crop could only occur through a direct stimu- 

 lation of the plants by traces of the disinfectant, or of its 

 decomposition products. On the other hand, the fact that 

 the action of the disinfectant depends upon the amount 

 added to the soil, larger doses giving greater crops than 

 smaller, led Moritz and Scherpe to adopt the view of Hiltner 

 and Stormer, that the chief effect of the disinfectant lies in 

 the alteration of the bacterial flora. The balance of the 

 microbiological flora is destroyed, the species are reduced, 

 but to different extents, and a way is opened for the develop- 

 ment of a new flora derived from the more resistant mem- 

 bers of the original flora. The great subsequent multipli- 

 cation of the bacteria results in a strong decomposition of 

 the insoluble nutrients, and partly through this, and partly 

 because of the increased activity of the nitrogen-gatherers, 

 much assimilable nitrogen is made available for the crop. 

 This is shown by the increased luxuriance of the foliage and 

 by its dark green colour. 



Hiltner and Stormer appear to think that the increase 

 in the available nitrogen is partly due to the greater fixation 

 of free nitrogen, and partly to the unlocking of the great 

 store of soil nitrogen. The altered nitrogen, they consider, 

 is converted into bacterial protoplasm , which being insoluble, 

 is not immediately available, but becomes so during the 

 the second season. Kruger and his pupils 1 found an 

 increase some time after treatment, which they believed 

 to be traceable to the increased growth of Azotobacter and 

 similar bacteria. Stormer 2 considered that the disinfectant 

 killed most of the inhabitants of the soil such as worms, 

 insects, spiders, lice, protozoa, mosses, algae, moulds and 

 bacteria, and that, during the first year, the nitrogenous 

 matter contained in the dead forms came into solution and 

 benefited the crop. 



1 Kruger, through Heinze, Cent. Bakt. 2 te., 16, 329. * Ibid., 20, 282. 



