TOXICITY OF HEAVY METALS 87 



as yet unable either to control or measure the former, excepting in a very 

 general way. 



In the third column are found the concentrations at which the different 

 salts inhibit germination for at least eighteen hours. When spores from 

 these cultures were removed from the toxic solution and placed in water 

 for a day, they germinated. The fourth column gives the maximum con- 

 centration in which germination occurred. In all cases this growth was 

 abnormal, showing swellings, swollen tubes and other unusual structures, 

 such as are illustrated in figs, i to 6. In the fifth column the concentrations 

 given are the maxima in which any normal germination was observed. The 

 sixth column presents the highest concentrations in which no toxic influ- 

 ence was manifest. 



From table IV it will be seen that the copper salts are by far the most 

 toxic of all the salts here studied. These two salts are very similar in 

 their effect on the germination of the spores, which is in accord with the 

 results of Clark [99], and points almost conclusively to the commonly 

 accepted idea that the toxicity of such copper salts is mainly or entirely 

 due to the copper ion. The last mentioned writer found that the concen- 

 tration of copper salts which inhibited germination were higher than those 

 producing the same effect in this investigation, a fact that may probably 

 be due to internal differences in the organisms dealt with; he found that 

 his five fungi varied markedly in their response to the same stimulus. Also, 

 Clark usually made use of nutrient media, while the present studies were 

 carried out without their employment. It is quite possible that the presence 

 of nutrient substances might have modified the effect of the poison. Dug- 

 gar 22 found the nitrate of copper considerably more toxic than the sulphate 

 and also considerably more so than it is here shown to be. In the work 

 of Stevens, 23 these two salts affected germination similarly and the concen- 

 trations required to prevent germination varied, with the different fungi 

 used, from 111/6400 to 111/200. Many other investigations of the effect of 

 copper on the germination of fungus spores have been carried out, with 

 varying results. The effect of this poison on algae has been studied by 

 Livingston [05]. Kahlenberg and True, 24 , Heald, 25 Jensen, 26 Szucs [12] 

 and others, have investigated its toxicity toward higher plants. The results 

 obtained indicate that fungus spores are considerably more resistant toward 

 the toxic effects of copper than are either the algae or higher plants. 



tfar, B.M., Physiological studies with reference to the germination of certain fungus spores. 

 Bot. Gaz. 31: 38-65. 1901. 



23 Stevens, F.L., The effect of aqueous solutions upon funtjus spores. Bot. Gaz. 26: 377-406. 1898. 



2J Kahlenberg, Louis, and True, Rodney H., On the toxic action of dissolved salts and their elec- 

 trolytic dissociation. Bot. Gaz. aa: 81-124. 1896. 



25 Heald. F.D., The toxic effect of dilute solutions of acids and salts upon plants. Bot. Gaz. 22: 

 I2S-IS3- 1896. 



28 Jensen, G.H., Toxic limits and stimulation effects of some salts and poisons on wheat. Bot. Gaz. 

 43: 11-44. 1907- 



