1918] AGEICULTURAL BOTANY. 427 



943, 9U, fig. 1; Jour. Son. Chem. Indua., S6 {J917), No. 1, p. //O).— Experiments 

 using A::otoba<'ter chroococewn and Clostrklium pasteurianum together are re- 

 ported. The nutritive medium used was composed of SO cc. drinking water, 

 20 cc. 5 per cent linseed extract, 2 gm. dextrose, 0.1 gm. potassium phosphate, 

 0.05 gm. magnesium sulphate, and 0.5 gm. calcium carbonate. Incubation at 

 from 21 to 22° C. lasted about six weeks. 



It was found that a close relation exists between the processes of assimila- 

 tion and disassimilation in the cell. The process of fixation of nitrogen ran its 

 course uninterruptedly until the available energetic substance was consumed. 

 The quantity of nitrogen fixed was relatively small (1.735 mg. of nitrogen per 

 gram of sugar decomposed), which is attriliuted to the low degree of activity 

 of the bacterial strains employed in the experiments. Nitrogen fixation and 

 sugar decomposition were parallel and showed a continuous increase throughout 

 the experiment, the maximum taking place in the period between the fifth and 

 fifteenth day. 



A comparison between the productivity of the work of the bacteria at differ- 

 ent periods of five days each showed that the process of nitrogen fixation was 

 at its best in the first period. " The efficiency of the bacteria declines rapidly 

 during the three following periods, after which, during the final period, it 

 remains at nearly the same level. It may be said, therefore, that during the 

 first periods of growth of the bacteria in question in the nonnitrogenous me- 

 dium, when the cells of the nitrogen fixers multiply energetically, their work 

 is most efficient. The impression of the hnv efficiency of the work of these 



microbes gained from examining the ratio — p at the close of the experiment 



must be due to the depressing influence resulting from the process being in its 

 last stages." 



Fixation of atmospheric niti'og'en by mixed cultures, V. L. OmeliInskii 

 {Arch. Set. Biol, [reiroarad], 18 {1915), No. J,, pp. 338-377, pi. 1; ahs. in Intrr- 

 nnt. Infit. Agr. [Home], Internat. Rev. Sci. and Pract. Agr., 7 {1916), No. 7, pp. 

 942, 943; Jour. Soc. Chem. Indtis., 36 {1917), No. 1, p. ^0).— Studies on the 

 fixation of nitrogen in cultures of a large number of races of Azotobacter and 

 Clostridium pasteurianum isolated from different Russian soils, associating 

 with them many other microorganisms usually accompanying them in soils, 

 are reported. 



It Is concludefl that " the study of the biochemical i-eactions by means of 

 which the bacteria in mixed cultures fix atmospheric nitrogen brings out 

 clearly the various aspects of the natural process occurring under conditions 

 of combined action of the different organisms. The organisms acting in com- 

 bination with the nitrogen-fixing bacteria in upper soil strata are very numerous 

 and they play an extremely important part in the life of the soil. The synergetic 

 activity of nitrogen-fixing and accompanying microbes is, both In laboratory 

 experiments and under natural conditions (cultivable stratum of the soil), of 

 a different character according to the properties of the species taking part In 

 the process and their environment. In other cases the function of the satellite 

 organism seems to consist in fixing the oxygen of the air and in creating the 

 anaerobic environment (for C. pasteurianum). The species added to the 

 cultures of nitrogen-fixing microbes sometimes supply the compounds of car- 

 bon needed for the process of fixing nitrogen as energetic substance. 



In the case of the combination. Azotobacter and C. pasteurianum, the 

 function of the former is not confined to fixing the oxygen of the air only 

 and consequently to creating an anaerobic environment for the Clostridiiim, 

 but this combination is also useful inasmuch as it destroys the injurious 



