28 



the lighter metal in this proportion produces the same ef- 

 fect as thovigh the 0.0001m copper ablution had been diluted 

 to two and a half times its original volume. 



Copper sulphate exhibits about the same toxicity 

 towards spores of Gleosporium as does the nitrate. A series 

 of combinations of this salt with Ca(N02)o, quite similar 

 to the series with Cu(K02)2 just described, gave no germin- 

 ation in the solutions containing O.OOOG3125m of the calcium 

 salt, while germination occurred in some of the cultures 

 containing 0.0000625ra of Ca(N03)2. In general, the effect of 

 CUSO4, either alone or in combination with Ca(NC3)2, was 

 practically the same as was that of Cu(N02)2« This furnish- 

 es some additional evidence toward the already rather firmly 

 established conclusion, that the toxicity of copper salts is 

 due to the cations and it also indicates the probability 

 that considerations bearing upon this toxicity need to deal 

 only with the cations. 



A series of experiments was carried out using O.OC04m 

 Cu(IT02)2 in combination with concentrations of Ca(N02)2 rang- 

 ing from 0.0C025n to 0.025m. The spores in these combinations 

 germinated readily in the presence of Ca(NC3)2 in concentra- 

 tions ranging from 0.001m to C.025m, but no germination was 

 found in combinations with O.CGOSm or C .0C029n of the calcium 

 salt. The form and abundance of germination with O.COlm 

 Ca(N02)2 "^as much the same as that found in O.0C004m of the 

 copper salt alone. Here a ratio of five molecules of tae 

 calcium salt to two of copper, the former occurring in the 

 solution at a concentration of 0.00C4m reduces the toxicity 



