10 



against the retarding action of the copper and the result is 

 a marked diminution in the poisonous action of ti.e copper." 

 They thus relate this influence of calcium upon copper to a 

 mutual effect of the two salts on the protoplasm. 



Gzucs^^ has recently shown thai the toxic effect of 

 copper sulphate on the roots of Cucurbita pepo may be inhib- 

 ited by certain concentrations of aluminum chloride. In this 

 case he used as index -f toxicity the ability of the root to 

 react to a geo tropic stimulus after it had been removed fEom 

 the poisonous solution. He varied the presentation time of the 

 toxic stimulus (copper sulphate) both alone and in combination 

 with aluminum, and found for the shorter time periods that the 

 presence of aluminum inhibited the poisonous action of the cop- 

 per. However, if such 5 combination of the two salts was allow- 

 ed to act for longer periods it also w&s toxic, in some cases, 

 and the roots lost their ability to resi;ond afterwards to a 

 geotropic stimulus. He used concentrations of copper sulphate 

 varying from 0.0C1875n to C.075n in combination with alum- 

 inum chloride in concentrations varying from 0.0C5n to 

 C.45n . The presentation time of the toxic stimulus ranged 

 from 33 minutes to 26 hours and 5C minutes. This writer 

 also studied the effect upon Spirogyra of quinine hydro- 

 chlorid, methyl violet and piperidin in combination 

 with various other substances. Tne toxicity of quinine 



10. Sz^cs, Joseph, Sxperimentelle Beitrage zu einer Taeorie 

 der antagonistischen lonenwirkungen. Jahrb. fur '.Vissenschaf t- 

 liche Eotanik 52:85-143, 1912. 



