722 EXPEEIMENT STATION RECORD. 



It is evident then that the organism can be freely distributed in dust by the 

 wind." 



A bibliography of 13 references to investigations on this subject is given. 



On nitrogen bacteria, H. Fischer (Verhandl. Natin'hist. Ter. Preuss. Rhcin- 

 lande, 62 (1905), pt. 2, pp. 135-145, pi. 1). — A study of tlie microscopic charac- 

 teristics and behavior in cultures of different forms of Azotobacter is briefly 

 reported and illustrated with several reproductions of microphotographs. 



Can fungi fix the free nitrogen of the air and increase the total nitrogen of 

 the soil? B. Heinze {Ann. Mycol., J, (1906), Ao. 1, pp. ',1-6S ; aha. in Centbl. 

 Bakt. [etc.], 2. Abt., 17 (1906), No. 8-10, pp. 266, ;36'7).— The author shows that 

 in addition to Azotobacter and Clostridium-like organisms there are many other 

 organisms which fix nitrogen, as for example, blue-green alg?e, which, however, 

 have a lower fixing capacity than Azotobacter. Whether molds have the power 

 of direct fixation is still questionable. Like the algjie, however, they aid the 

 nitrogen-fixing organisms by supplying necessary carbonaceous food. 



The formation of hydrocarbons of the acetylene series was observed in cul- 

 tures of Azotobacter. In the fixation of nitrogen the first assimilation prod- 

 ucts are thought to be amino acids and the second prol)ably salts of carbamin 

 acid. From the high molecular amino acids the protein compounds may be 

 gradually built up. 



Studies on nitrogen fixation in cultivated soils, P. Schneider (Landw. 

 Jahrb., 35 (1906), Sup. .'/, pp. 63-83, pij. 1). — A series of culture and pot experi- 

 ments with nitrogen-fixing bacteria (Azotobacter, etc.) and root tubercle organ- 

 isms (horse-bean bacteria and pure cultures for peas prepared by this Depart- 

 ment) in various media is reported. 



The conclusions reached from these investigations are that nitrogen-collect- 

 ing bacteria can fix amounts of nitrogen in the soil which are capable of being 

 determined by analytical methods. This fixation is greatly increased by the 

 addition of an organic source of energy such as mannite. glucose, etc., and is 

 promoted by an alkaline reaction, as for example, by the jiresence of a suitable 

 amount of lime. A calcareous soil is therefore especially favorable to the 

 development of nitrogen-collecting organisms. The fixation of nitrogen can 

 be very appreciably increased by the addition of potassium phosphate. Loose 

 texture of the soil, permitting good aeration, also increases it. Root tubercle 

 bacteria which had been grown on powdered chalk were more active as inocu- 

 lating material than those which had been grown on gelatin. 



Some observations on nitrification, S. F. Ashby (Jour. Agr. 8ci., 2 (1907), 

 No. 1, pp. 52-67). — A series of observations on substitution of other bases, ferric 

 hydrate and iron rust, for calcium carl)onate ; nitrification of ammonia ab- 

 sorbed by clay and peat; direct nitrification of a neutral ammonium salt; 

 and the influences of ammonium salts and asparagin upon the oxidation of 

 nitrites to nitrates by Nitrobacter, is reported, the results leading to the fol- 

 lowing conclusions : 



" Carbonates are not the only substances in the soil which serve as bases for 

 nitrification, since a marked nitrification of an ammonium salt can be brought 

 about in the presence of ferric hydrate, either in the freshly precipitated state 

 or as ' iron rust.' In solutions nitrification is not completed with this sub- 

 stance, probably because the ferric nitrite or nitrate formed dissociates and the 

 solution becomes acid. 



"Neither kaolin nor modeling clay serves as a base for nitrification. 



" The double ammonium combination formed by the absorption of ammonium 

 salts by modeling clay can most probably be nitrified in the absence of any 

 base, but the corresponding combination with peat undergoes no nitrification 

 in the absence of a base. 



