SOILS FERTILIZERS. 815 



ground were examined for Azotobacter, but always with negative results. In 

 the cases in which it was looked for in arable soils in the immediate vicinity 

 of woods whose soil did not contain any species of Azotobacter its presence 

 was easily demonstrated, but the species was always A. chroococcum." 



The following general conclusions are drawn : "Azotobacter is only excep- 

 tionally present in Danish forest soils. In some localities in which the soil 

 contains much calcium carbonate A. heijerinckii and A. vitreum are present. 

 Consequently, for the supply of nitrogen to the forest soils of Denmark some 

 other micro-organisms, probably lower fungi, must be of importance. . . . The 

 culture of Azotobacter in Beijerinck's nutritive solution in which the lime is 

 replaced by 5 gra. of the soil to be studied is a rapid and easy way of showing 

 if a woodland to be regenerated requires lime or not since the calcium com- 

 pounds that favor the development of Azotobacter iii such cultures seem to 

 be the same which facilitate the development of those organisms which lead 

 to the production and conservation of a good mold and favor the development 

 of forest trees, especially of beeches." 



A report along similar lines by Christensen is noted above. 



The nonsymbiotic nitrogen-fixing' soil bacteria and their importance in 

 natural economy, M. DtiGGEU (Naturw. Wchnschr., 30 (1915), No. Jf2, pp. 651- 

 66Ii). — Tlie author discusses the physiology and activity of the nonsymbiotic 

 nitrogen-fixing soil bacteria, with special reference to their relation to soil 

 fertility. 



The fixation of potash by soil bacteria, S. Kyropottlos {Ztschr. Gdrungs- 

 physiol., 5 {1915), No. 3, pp. 161-166; ahs. in Internat. Inst. Ag7\ [Rome'], Mo. 

 Bui. Agr. Intel, and Plant Diseases, 6 (1915), No. 10, pp. 1306, iSOr).— Studies 

 of the potash-fixing powers of soil bacteria in soil and solution cultures, 

 using cane sugar as the nutritive medium in soil and the Beijerinck nutritive 

 solution, showed, with different potash additions, no analytical proof of the 

 assimilation of any considerable amounts of potash by bacteria. 



The antizymotic action of a harmful soil constituent: Salicylic aldehyde 

 and mannite, J. J. Skinneb (Pla7it World, 18 (1915), No. 6, pp. 162-161).— 

 Experiments with wheat in distilled water and in nutrient solution cultures 

 to determine the influence on the crop growth of mannite alone and in com- 

 bination with salicylic aldehyde are reported. Mannite was used alone in con- 

 centrations varying from 10 to 200 parts per million in distilled water, and in 

 a concentration of 100 parts per million in nutrient solution. In the distilled 

 water cultures *' growth in some of the mannite concentrations was about equal 

 to that in pure distilled water. Some of the cultures produced larger growth 

 and others made less growth than in distilled water." It was further found 

 that " the mannite in the nutrient solutions containing all three of the nutrient 

 elements underwent decomposition, there was a formation of nitrites and 

 ammonia, and consequently the decomposition caused poor plant growth. The 

 solution in which there was no phosphate was not a good medium for the devel- 

 opment of bacteria, consequently there was no decomposition of the mannite. 

 Mannite as such does not seem to be harmful to wheat seedlings, and when 

 decomposition does not take place the material would seem to be used by the 

 plants and an increased growth results." 



In further wheat-culture experiments in nutritive solution to which mannite 

 was added in amounts of 100 parts per million and salicylic aldehyde in 

 amounts of from 1 to 100 parts per million, it was found that " nitrites and 

 ammonia formed in the duplicate mannite solutions and in those solutions 

 which contained mannite together with 1, 5, and 10 parts per million of sali- 

 cylic aldehyde. In the solutions which had no plants 25 parts per million and 



