222 president's address. 



referred, he succeded, as we saw, in isolating a micro-organism 

 which only possesses the power of converting nitrous acid into 

 nitric acid ; it cannot attack ammonia and convert it into 

 nitrous acid. The former may be called the nitric ferment, 

 and the nitrification of the soil with its aid is clear. It is 

 brought about by two independent organisms, the first pro- 

 ducing nitrous and the second nitric acid. 



The scanty presence of nitric acid in the soil does not, how- 

 ever, prevent Professor F. Frankland from suggesting that the 

 immense deposits of nitrate of soda in the rainless districts of 

 Chili and Peru are the result of " a gigantic nitrification pro- 

 cess at some previous period of the earth's history," and that 

 "the nitrifying organisms then and there" must have been 

 endowed with " very much greater powers than they possess to- 

 day." Moreover, the nitrifying organisms now found can build 

 up living protoplasm in a solution from which organic matter 

 has been rigorously excluded; and, therefore, can only have 

 been elaborated by carbonic acid as the source of protoplasmic 

 carbon, and from ammonia, and nitrous or nitric acids as the 

 source of protoplasmic nitrogen — and if this be accurate and 

 is subsequently confirmed it represents a new phase in our 

 knowledge of the functions of plants without chlorophyll. 



In the same way there is an excess of nitrogen in leguminous 

 crops which cannot be accounted for by the combined nitrogen 

 supplied to the land in the shape of manures and in rain 

 water ; but it has been shown that this excess of nitrogen is 

 largely dependent on the presence of certain bacteria flourish- 

 ing in and around the roots of these peas, beans, vetches and 

 their like, and these tuberosities are found, not only to be rich 

 in nitrogen, but to harbour swarms of bacteria. 



We have long been accustomed to think of bacteria as active 

 agents in putrefaction, and the various ferments ; to be the 

 virus of many and terrible diseases in man and animals. Nay, 

 they infest the water we drink, the food we may eat, even the 

 tobacco we smoke, the butter of our breakfast tables, and the 

 very air we may breathe ; but it is a comparatively new role 

 for their activity that the essential processes of vegetable 

 physiology are brought about by their agency, redeeming to 

 some extent the adverse influences they so generally exert. 



