2/0 



In studying the conversion of nutritive substances and their transfor- 

 mation by soil bacteria, the process of the storage of nitrogen, i. e., the assim- 

 ilation of free nitrogen by bacteria, is to be considered. Besides the anaerobic 

 Clostridium Pastorianum (Pasteurianum), determined some time ago by 

 VVinogradski, which with sufficient amounts of carbo-hydrates can make 

 use of the atmospheric nitrogen for its nutrition, — aerobic species have been 

 found by Beijerinck such as Asotohacter chroococcum. This species, present 

 in every field soil, consumes extremely large amounts of carbo-hydrates by its 

 nitrogen assimilation (according to Gerlach and Vogel 8.9 mg. nitrogen in 

 I gram grape sugar). 



The changes in forest litter should be included liere. The nitrogen en- 

 richment due to them has been caluculated by Henry \ He emphasizes that 

 nitrogen is stored up with the decomposition of dead oak and beech 

 leaves and spruce needles. This decomposition is very active on damp soil in 

 summer, but scarcely noticeable in winter, or when mixed with soil. Ac- 

 cording to his calculations, fallen oak leaves accumulate 20 kg. of nitrogen 

 per hectare within a year. On dry soil the dead foliage either does not be- 

 come enriched at all (in the red beech), or only very insignificantly (white 

 beech, spruce). In no case, however, was any loss of nitrogen noticed. 



The active enrichment of the soil by the symbiotic tubercle-forming 

 bacteria should also be mentioned here. Cultures of these bacteria liave been 

 introduced into commerce under the name "Nitragin"- and cultures of non- 

 symbiotic nitrogen gatherers are sold under the name "Alinit.'* More recent 

 investigations indicate that not only bacteria of the same species adapted to 

 individual host plants may be assumed, but that even different species may 

 be distinguished. Hiltner contrasts two species chiefly on account of their 

 morphological and physiological differences ; viz., Rhizohium radicicola and 

 Rh. Beijerinckii. The activity of these tubercle bacteria in their relation to the 

 Leguminoseae begins only when the Leguminoseae have suffered for some- 

 time from nitrogen hunger and they are inactive when nitrates are present in 

 the soil. This should be mentioned only in passing to illustrate further the 

 dependence of bacterial life on various factors. The root secretion of each 

 plant must also count as such a factor. Even the very healthy seeds which 

 get into the soil and the green parts of healthy seedlings have a specific bac- 

 terial flora, which can increase greatly and swarm out into the soil. Other 

 micro-organisms can be pressed back by these^. From such inequalities of 

 the growth conditions in the soil must arise necessarily significant fluctua- 

 tions in the individual number of each species of bacteria and thereby in the 

 whole achievement so far as the production of nutriment favorable for culti- 



1 Henry, E., Ueber die Zersetzung- der abgefallenen Blatter im Walde etc. (Annal. 

 Sc. Agron. franc. VIII). cit. Centralbl. Agrik. Chem. 1904, p. 703. 



2 In regard to soil inoculation, it should be taken into consideration that bac- 

 teria, lilve all plants, will thrive only when the soil is so constituted that it favors 

 their increase. As Homy has very characteristically expressed it, "they must find 

 their proper soil climate." 



3 Diigg-eli, M., Die Bakterienflora gesunder Samen etc. Centralbl. f. Bakt. II. 

 1904, Vol. XIII, p. 198. 



