iqiq] BON AZZI— nitrification 195 



The bacilli are shorl, of a slightly oval shape, and vary from i . i /x to i . 7 /x 

 in length; they are about 0.8-0.9/M broad. They are grouped characteris- 

 tically in irregular clumps and are held together by a jelly-like material. 

 Each aggregation is indeed a tj^pical zooglea. The aggregations of bacteria 

 were found chiefly in the bottom of the flasks, as was also the case with the 



organism described by Winogradsky On one important point there 



appears to be a difference between our results and those reached by the above 

 mentioned investigators. The organism discovered by them oxidizes ammonia 

 to nitrite, but carries it no further. Our flasks give complete oxidatton to 



nitrate We are not even prepared to say that there may not have 



been a mixture of two or more species in our flasks, all agreeing closely in 

 morphological characters, and in giving no growth on gelatin, but diftering 

 in important physiological respects. 



This statement makes it quite clear that probabh' their cul- 

 tures were a mixture of the two forms isolated and separated by 

 WixoGRADSKY (ii). No lengthy description of the organisms 

 isolated by the Russian investigator is here necessary, and a sum- 

 mary review of his findings (12) will suffice. The nitrite-forming 

 organisms from difterent parts of the world were divided by Wino- 

 GR.ADSKY in two genera and several species as follows: Nitroso- 

 monas {N . europeac and N. javaniensis), from the Orient; and 

 Nitrosococcus, from the Occident. Nitrosomonas received by far 

 the greatest attention from .Winogradsky, while Nitrosococcus^ 

 which is most important to American economy, he only incom- 

 pletely described. The soils from which Winogradsky isolated 

 his Nitrosococciis were from Campinas (Brazil), Quito (Ecuador), 

 and ^Melbourne (Australia). 



Samples of NortH American soils were not studied, and it is 

 surprising that no description of organisms from such soils has 

 been attempted since the time of the discovery of the active agents 

 of nitrification. It is true that Jordan and Richards gave a 

 description of the sewage organisms they were working with, but 

 their description does not conform to the one given by Wino- 

 gradsky of the South American organisms. It is evident, there- 

 fore, that, were it only from a geobotanical standpoint, the 

 description of the organisms from the Northern Hemisphere 

 presents some importance.^ 



3 The investigations reported by Owen, W'u. L. (The efYect of carbonates upon 

 nitrification. Georgia Exper. Sta. Bull. Si. 1-42. 1908), should not be overlooked 

 in this connection. Unfortunately it must be admitted that the photographic repro- 

 ductions of the organisms which he found in his flasks remind us only of a mixture of 



