30 Livingston : Chemical stimulation of a green alga 



I VI AX STRENGTH 



A comparison of the above lists will make it clear at once that 

 there is only a very general agreement between them. In the 

 present state of our knowledge nothing more need be said. 



The literature of the effect of toxic substances on higher 

 plants, although more extensive, is in a more unsatisfactory state 

 than that concerning the lower ones. It would be somewhat out 

 of the field of the present paper to go here into detail as to the 

 concentrations which accelerate growth and those which kill 

 higher plants. It is well established that most of the metals, 

 when at the right strength, do accelerate growth of seedling 

 roots, but there is discrepancy among the several observers as to 

 the limits. The same is true of fatal doses. Kahlenberg and True * 



* Kahlenberg, L. & True, R. H. On the toxic action of dissolved salts and 

 their electrolytic dissociation. Bot. Gaz. 22 : 81-124. 1S96. 



