TOXICITY OF HEAVY METALS 91 



A consideration of the toxicities of the single salts,~aa brought out in 

 this investigation, also suggests that the influence of each one of these salts 

 upon the protoplasm of the spore is specific. The nitrates of lead and 

 aluminum, in concentrations somewhat below those which inhibit germina- 

 tion, frequently produce within the spore (either directly or indirectly) a 

 dark, chlamydospore-like body. The presence of copper, at a similar con- 

 centration as regards toxicity, causes a granular appearance of the proto- 

 plasm and much the same effect was observed in concentrations of nickel 

 nitrate not quite strong enough to inhibit germination. Toxic concentra- 

 tions of zinc nitrate, however, fail to produce any visible alteration in the 

 protoplasm. The effects of the different single salts upon the spores are 

 therefore not at all the same, and it seems at least reasonable to suppose 

 that the requisite antidotes may not be identical and may not be effective 

 in the same manner in all cases. A given substance at a given concentration 

 may inhibit the poisonous effects of one toxic salt and yet have no influ- 

 ence upon the toxicity of another. Thus, neither calcium nor magnesium 

 nitrate exerts any apparent influence upon the toxic effect of aluminum 

 nitrate, but both are markedly effective in counteracting the toxicity of the 

 corresponding salts of zinc and lead. 



The conclusion seems unavoidable, therefore, that no simple and broadly 

 general explanation can be applied to these exceedingly various antagonistic 

 actions, and that the explanation of each particular case must involve 

 the chemical characteristics of the salts concerned and the physico-chemical 

 properties of their solutions. The exceeding complexity of the material 

 system within the cell must make possible a great variety of explanations 

 until this variety becomes further limited by increased knowledge. As has 

 been well emphasized by Osterhout [13] the future advance of our knowl- 

 edge of this intricate subject must depend solely upon further investigation 

 of a quantitative nature. 



THE LABORATORY OF PLANT PHYSIOLOGY 

 OF THE JOHNS HOPKINS UNIVERSITY. 

 APRIL i, 1913. 



LITERATURE CITED. 



Numbers in brackets throughout the preceding pages refer to the year of publi- 

 cation and to the corresponding numbers which follow authors' names in this list. 



Acree, S.F. [n]. See Loomis and Acree [n]. 



Bartlett. H.H. [12]. See True and Bartlett [12]. 



Clark, J.F. [99], On the toxic effect of deleterious agents on the germination and development of cer- 

 tain filamentous fungi. Bot. Gaz. 28: 280-327, 378-404. 1899. 



[01], On the toxic value of mercuric chloride and its double .salts. Jour. Physic. Chem. 5: 



289-316. 1901. 



- [02], On the toxic properties of some copper compounds wth special reference to Bordeaux 

 mixture. Bot. Gaz. 33: 26-48. 1902. 



