TOXICITY OF HEAVY METALS 61 



a combination of the two salts was allowed to act i&c longer periods, rt 

 also was toxic in many cases, and the roots lost their ability to respond 

 afterwards to the geotropic stimulus. He used concentrations of copper 

 sulphate varying from o.ooi875n to o.o75n, combined with aluminum chlor- 

 ide in concentrations varying from o.(X>5n to o.45n. The presentation time 

 of the toxic stimulus ranged from 33 minutes to 26 hours and 50 minutes^ 

 This writer also studied the effect upon Spirogyra of quinine hydrochloride, 

 methyl violet and piperidine in combination with various other substances. 

 The toxicity of quinine hydrochloride was altered by various concentrations 

 of other substances, being almost inhibited by aluminum nitrate, markedly 

 decreased by calcium nitrate, and only slightly lessened by potassium nitrate. 

 Thus, the effectiveness of these salts in reducing the toxicity of quinine 

 hydrochloride diminished with the valency of the cation. Similar results 

 were obtained with the same series of salts in combination with methyl 

 violet. The effect of combinations of various substances with piperidine 

 was, in most cases, markedly to increase its toxicity. Sziics apparently 

 considers the antagonistic action, as investigated by him, to be due to the 

 lowering of the rate of absorption of the toxic ion by the presence in the 

 solution of another ion of similar sign. He concludes, in summarizing: 

 " Die Ursache der ' antagonistischen lonenwirkungen ' liegt in alien von mir 

 untersuchten Fallen in der gegenseitigen Beeinflussung der Aufnahmege- 

 schwindigkeit zweier im gleichen Sinne geladener lonen." 



From the results obtained in the investigations just considered, it is 

 apparent that the toxic effect of the heavy metals on an organism can 

 be modified, in some cases at least, by the addition of certain salts in 

 proper concentration. True and Gies, and Sziics, working with higher 

 plants, attribute this influence of one salt on the effect of another to a 

 simultaneous action of the two salts upon the organism itself, while Clark, 

 working with fungi, relates the inhibition of the toxic effect of heavy 

 metals in combination, to some modification of the salts in the solution. 

 The proportions of salts used in the investigations just mentioned were 

 widely different, and it is of course possible that the different conclusions 

 reached may have been due to this feature. Furthermore, as fungi and 

 higher plants so frequently react differently to the same stimulus, it is 

 possible that one of these two explanations might hold for one group of 

 organisms and the other for the other group. The present study, in which 

 a fungus was employed, was undertaken partly to throw light on the 

 question just suggested. 



It was the purpose of this research to examine the effects of the nitrates 

 of copper, lead, zinc, nickel, and aluminum, upon the germination of 

 fungus spores, the salts of these heavy metals being used both alone and 

 in combination with the nitrates of calcium and magnesium, to see whether 



