DISTRIBUTION 217 



2 streptothrices, and 2 fungi (a Fadenpilz and a Schimmelpilz) . 

 These showed no polymorphism, but all retained constant char- 

 acters. 



In 1902 Chester summarized the knowledge on nitrification as 

 follows: 



1. That nitrification in the soil is caused by a distinct or rather 

 by two distinct organisms possessing certain definite characters. 



2. That these organisms will not grow in the presence of any 

 considerable amount of organic matter, and that all reported 

 attempts to cultivate them on ordinary organic media are without 

 authentication. 



3. That the above nitrifying organisms are found abundantly 

 in all cultivated soils and in ordinary soil water containing a due 

 proportion of ammonium carbonate, sulphate, etc., they find a favor- 

 able medium for their development. 



4. That the result of such development is: (a) The conversion 

 of ammonia into nitrous acids through the agency of the nitrous 

 organism; and (b) the immediate conversion of the previous nitrous 

 into nitric acid by means of the equally abundant nitric ferment. 



Distribution. Probably the nitrifying bacteria were some of the 

 first living organisms to appear upon this planet, and even yet 

 they act as the pioneers preparing the soil for other plants. Muntz 

 has found the decayed rocks of Alpine summits, where no other 

 life exists, swarming with the nitrifying ferments. The limestones 

 and micaceous schists of the Pic du Midi, in the Pyrenees, and the 

 decayed calcareous schists of the Faulhorn, in the Bernese Ober- 

 land, offer good examples of this kind. The organisms draw their 

 nourishment from the nitrogen compounds brought down in snow 

 and rain; they convert the ammonia into nitric acid, and this in 

 turn corrodes the calcareous portions of the rock. Stiitzer and 

 Hartleb have observed a similar decomposition of cement by 

 nitrifying bacteria. 



The nitrifying bacteria appear to be very widely distributed 

 Muntz and Aubin have observed their presence not only in all 

 cultivated soils which they have examined, but also in those of 

 deserts. They are not usually found in the air or in rain water. 

 River water and sewage contain them. They are usually present 

 in well waters. In the case of deep wells their origin is due to 

 surface soil or to drainage from the surface soil which has found 

 its way into the well, the water of deep wells not being their natural 

 habitat. Thomasen found the nitrite organism in samples of 

 ooze from the bottom of the Kiel Fjord, but not in the sea water 

 nor on the Plankton or the fixed algae. It was also found in similar 

 samples of soil from the vicinity of Helgoland and in slime from 

 the bottom of the Bay of Naples, but only in samples taken near 

 the land. 



