158 



Commencing then with matters agricultural, or rather agri- 

 culturally chemical, it has become apparent in recent years that 

 many old ideas must be discarded. The vague notion that it is 

 only necessary to supply to the soil in any fashion the chemical 

 constituents which go to make up the plant has been of necessity 

 abandoned, and it has been found that almost as much care and 

 attention must be bestowed on feeding plants as on feeding 

 animals, not only with respect to the nature of the food supplied. 

 but also with reference to the manner of its administration and 

 the conditions under which the food becomes assimilable. 



Every schoolboy knows that nitrogen must be supplied to^ 

 plants, but nothing has caused more discussion and given rise to 

 more experiments than the questions whence and how plants 

 obtain their supply of this substance. It has been known from 

 time immemorial that such substances as stable manure, sewage,, 

 tfec, which when exposed to air decompose, and give off ammonia, 

 are capable when added to the soil of yielding a supply of 

 nitrogen to plants, but till comparatively recently it was not 

 known by what series of processes the nitrogen is made available 

 for use. It became known, however, that all fertile soils contain 

 nitrates, and further, that nitrates are formed m soil under 

 certain conditions, from such substances as I have already re- 

 ferred to, stable manure, sewage, .fee. With these data as a 

 starting point investigations were undertaken, which led to- 

 remarkable and interesting results. In a paper published in the 

 journal of the Chemical Society of London for 1891, Warington, 

 who was associated as chemist with Gilbert and La wes, in their 

 world-famed experiments at Rothamstad, in England, summarises 

 the results of experiments carried out chiefly by himself, the- 

 principal of which are these : — 



1. There are present in fertile soils minute organisms of a^ 

 bacterial nature, which convert ammonia into nitrates. 2. These 

 organisms are aerobic, and are not found at depths greater than 

 about 6 ft., or perhaps less. 3. The ammonia is first converted 

 into nitrates by a special organism (nitrosomonas), which, how- 

 ever, is incapable of converting nitrites into nitrates, or of 

 directly converting ammonia into nitrates. 4. The growth of 

 this organism, and therefore its activity, is promoted by the- 

 presence of carbonic acid, sodium bi carbonate, and some other 

 substances containing carbon, the carbon being apparently neces- 

 sary to provide for its growth and multiplication. Ordinary 

 sodium carbonate, however, greatly hinders the action of this 

 organism. 5. There is another organism in fertile soil (nitro- 

 bacter), which is capable of energetically converting nitrites into 

 nitrates, but is not capable of directly converting ammonia into 

 nitrites or nitrates. 6. The growth of this organism is also, as- 



