12 Influcnce of Arsenic in Solls [Oct. 



also, when present to the extent of only i part per ten million of 

 water. Although Russell" states that it is not as toxic in soll as 

 in water, he and Darkshire^ found it to be toxic in soils; and they 

 failed to get a stimulating influence witli it. Montemartini^ has 

 noted a Stimulation with copper sulphate when used in dilute Solu- 

 tions. This, however, may have been due to the anion and not to 

 the cation, as sulphates do stimulate plant growth by their action on 

 insoluble constituents of the soil.^ Clark and Gage^° have found 

 that very dilute Solutions of copper have an invigorating influence 

 upon bacterial activity. In order that any Stimulation may be noted, 

 the copper must be present in very small quantities. Jackson^ ^ 

 found that i part of copper sulphate in 50,000 parts of water killed 

 B. coli and B. typhosus. Kellerman and Beckwith^^ found that the 

 common saprophytic bacteria are more resistant to copper than is 

 B. coli; their results also show stimulating influences at some con- 

 centrations. So it is likely that both the copper and arsenic stim- 

 ulated in these experiments. 



With all the other Compounds tested there was either a marked 

 or very slight Stimulation. This is in keeping with the findings of 

 other investigators. Johnson^ ^ found that arsenic, in dilute Solutions, 

 stimulated seeds, while Bouilhac^^ found that it stimulated algae. 

 Stimulation of nitrification may be due either to the arsenic inhibit- 

 ing or killing injurious species, or to a direct Stimulation. It seems 

 remarkable that bacteria should function in the presence of the 

 large quantities of water-soluble arsenic which were present in 

 some of these tests. One would be prone to ascribe the nitrifica- 

 tion to something other than a biological influence, were it not for 

 the fact that Gosio^^ grew moulds in organic matter containing 



ß Russell : Soil Conditions and Plant Growth ; New York and London, 

 1912, p. 47. 



'' Russell and Darkshire : Jour. Agr. Sei., 1905, i, p. 261. 



8 Montemartini : Bull. Agr. Bur. Intel, and Plant Diseases, 191 1, ii, p. 2467. 



8 Greaves : Jour. Biological Chem., 1910, vii, p. 298. 



^•^ Clark and Gage: Jour. Inject. Diseases, 1906, ii, p. 175. 



11 Jackson : Jour. Anter. Chem. Soc, 1905, xxvii, p. 675. 



12 Kellerman and Beckwith : U. S. Dep. Agr., Bur. Plant Ind., Bull. 100, p. 57. 

 13 Johnson: Exp. Sta. Record, i896-'97, viii, p. 232. 



i*Bouilhac: Ibid., iSg^-'oo, xi, p. 1916. 



i^Gosio: Lafar's Technical Mycology; Trans, by Salter, 1911, ii, p. 37. 



