THE NITROGEN CYCLE 469 



growth, the effect of the antiseptic must have been directly 

 on the plants. 



388. Hiltner and Stormer's theory. — According to 

 Hiltner and Stormer, 1 the effect of treatment with carbon 

 bisulfide is to cause a disturbance in the equilibrium of 

 the different forms of soil bacteria. These investigators 

 compared the numbers in three groups of bacteria that 

 developed on gelatin plates inoculated from soil infu- 

 sions. The groups were Streptothrix, liquefiers, and 

 non-liquefiers. The normal relation of these in the soil 

 with which they worked was 20 per cent Streptothrix, 

 5 per cent liquefiers, and 70 per cent non-liquefiers. After 

 treatment with carbon bisulfide the relative proportions 

 were 5 per cent, 10 per cent, and 85 per cent, respectively. 

 From 70 to 75 per cent of the whole number of bacteria 

 were destroyed by the treatment, but the numbers rapidly 

 increased after treatment, rising in a few weeks to 50,- 

 000,000 to a gram in a soil that contained 10,000,000 to a 

 gram before treatment. This increase is due largely to 

 the development of the non-liquefiers, the Streptothrix 

 remaining at about the same actual number. 



The fact that the equilibrium of the bacterial flora 

 was so greatly disturbed by the treatment with carbon 

 bisulfide led Hiltner and Stormer to believe that the greater 

 productiveness of the soil after treatment is due to the 

 greater effectiveness of the surviving and rapidly develop- 

 ing forms in rendering available the supply of plant 



1 Hiltner, L., and Stormer, K. Studien iiber die Bakteri- 

 enflora des Ackerbodens, mit besonderer Berucksichtigung 

 ihres Verhaltens nach einer Behandlung mit Schwefelkohlenstoff 

 und nach Brache. Arb. Biol. Abt. f. Land- u. Forstwirtschaft 

 am Kaiserl. Ges. Amt., Band III, Heft 5. Berlin, 1903. Ab- 

 stract in Centrlb. f. Agrikultur Chemie, 33 Jahrg., Seite 361- 

 374. 1904. 



