526 EXPERIMENT STATION RECORD. 



The experiments were made with BacUlufi prodigmsus and with mixed bacteria 

 of the same soil from which the extract tested was obtained. The toxic action 

 was greater with B. prodigiosus than with the mixed soil bacteria. In other 

 words, the latter exhibited a certain degree of immunity toward their own 

 toxins. 



It is claimed that the toxin contained in the soil is soluble in dilute saline 

 solutions, is partially destroyed at 94° C, rapidly decays in aqueous solution, 

 is converted by boiling into a nutrient, is destroyed by sunlight, and will decay 

 during storage of the soil in an air-dry condition. The power of the toxins is 

 not diminished by sodium chlorid, potassium sulphate, or magnesium sulphate 

 solutions, as the toxic effects of extracts of soil made with a 0.5 per cent solu- 

 tion of these compounds were very pronounced. 



It is also stated that soil particles have a protective covering of soil wax, 

 or agricere, which consists of saponifiable and unsaponifiable residual organic 

 matter of the soil. When disinfectants are applied to the soil, such as carbon 

 bisulphid, chloroform, etc.. their action is a double one. They kill off the less 

 resistant bacteria, and dissolve agricere and carry it to the surface of the soil, 

 thereby removing the waterproofing from the soil particles, and thus enabling 

 the surviving bacteria to obtain a greater food supply. Heat, it is claimed, 

 destroys the toxins and the less resistant bacteria, thus permiting the more 

 resistant species to multiply very rapidly, due to the absence of the soil bac- 

 teriotoxins. 



Experiments on ammonia and nitrate formation in soils, II, J. G. Lipman, 

 P. E. Brown, and I. L. Owen {Centhl. Bakt. [etc.^, 2. AM., 30 {1911), No. 

 1-12, pp. 156-181). — In an earlier communication (E. S. R., 23, p. 621) the 

 authors showed that ammonia formation may serve as an index of the intensity 

 of decomposition processes in the soil. In this paper further tests of the accu- 

 racy of this method and additional data on the decomposition of protein com- 

 pounds in the soil are reported, including detailed studies on ammonia forma- 

 ion from dried blood as affected by the mechanical composition of the soil, 

 ammonia production as affected by moisture relations, the relations of lime to 

 ammonification in soils, and the influence of chemical and physical factors on 

 ammonia formation. 



Taken as a whole, the experiments reported furnished convincing evidence, so 

 the authors claim, as to the accuracy of the method employed, that is, of using 

 the formation of ammonia as a criterion of the intensity of the decomposition 

 processes in the soil. 



On the role of nitrate reduction in the metabolism of denitrifying bacteria, 

 O. Wegner {Welche Rolle spiclt die Nitratreduktion im Stoffwechsel der de- 

 nitriflzierenden Baktericnf Inaug. Diss., Univ. Berlin. 1910, pp. 32; abs. in 

 Bot. CentU., 116 (1911), No. 10, pp. 267. 26'8).— The experiments here reported 

 were carred on with Bacterium actinopelte in culture media containing peptone, 

 hemoglobin, and albumin as a source of nitrogen, but containing no amid 

 substances. 



The addition of galactose, levulose, and dextrose to the culture media stimu- 

 lated the growth of the fungi and the reduction of the nitrates and nitrites to 

 nitrogen. The amount of calcium nitrite in the culture media did not exceed 

 1 per cent, but the most intense nitrite decomposition occurred in a 0.25 per 

 cent solution. 



In the decomposition of nitrates by the bacteria 2 stages occurrred, viz, first, 

 the change from nitrate to nitrite, and second, the reduction of the nitrites to 

 free nitrogen and nitrous oxid. It was found that anaerobic conditions in 

 the culture media greatly increased the nitrite reduction. 



