TOXICITY OF HEAVY METALS 75 



have been observed, and the protoplasm usually appears markedly granular. 

 The spores were transferred from the poison solution to a new drop cul- 

 ture with distilled water and were then returned to the thermostat. At 

 the end of twenty-four hours, observation showed that many of the gran- 

 ular spores had germinated normally, although the granular appearance was 

 still very noticeable. Further proof that the granulated appearance with 

 which we have here to deal is not a post mortem effect of copper poisoning 

 may be derived from the fact that the germinal tubes of spores which 

 had germinated in a combination solution of o.oooim Cu(NO 3 ), and 

 o.oooo6m Ca(NO 3 ) 2 elongated considerably when the cultures were allowed 

 to remain in the thermostat for a second day, although the spores showed 

 the characteristic granulation above mentioned. 



It seems probable, from these and other similar lines of evidence, that 

 the copper of the solution penetrates the spore wall and gives rise to the 

 precipitation or coagulation effect just described. 



It may be noted here that the influence of calcium upon the toxicity of 

 copper is of interest in connection with the problem of fungicides and fungi- 

 cidal action. From the results obtained in the experiments described above, 

 the conclusion seems warranted that only a small portion of the soluble 

 copper in Bordeaux mixture is effective as a fungicide. Yet it is a well 

 known fact that a long list of fungous diseases, including apple bitter-rot, 

 can be controlled by the proper applications of this mixture to the host 

 plants. The use of KOH instead of Ca(OH) 2 in preparing the fungicide 

 should result in a much more toxic mixture, for, as brought out in the 

 preceding experiments, potassium is only about one fourth as effective as 

 calcium in decreasing the toxicity of copper. From the standpoint of 

 the host, however, it is quite probable that this anti-toxic effect of the 

 calcium is important in preventing " spray-injury " to the foliage and fruit, 

 while the small amount of soluble copper present, is, in most cases, suf- 

 ficient to prevent fungous growth. 



Lead. 



The nitrate of lead is considerably less toxic toward the Gloeosporium 

 spores here employed than is that of copper. The concentration just 

 inhibiting germination after eighteen hours was found to be about o.QO4m. 

 With a concentration of 0.002111 of the lead salt, some of the spores showed 

 slight terminal or lateral swellings. At this concentration spores were fre- 

 quently found in which one half was brown or blackened while the other 

 seemed devoid of protoplasm, appearing as if the protoplasmic contents 

 had all collected in one end and had then taken on a thicker wall. No 

 increase in size or local swelling was apparent in such cases. In a con- 

 centration of o.ooim the blackened bodies just mentioned were found, as 



