65 



Clark, working with fungi, and Livingston, with an alga, 

 found nickel salts to be more strongly toxic than those of 

 zinc, a result which is opposite to that obtained in this 

 investigation. 



Magnesium, calcliim, and potassium nitrates and cane 

 sugar end the list, in the order named. It is noticeable 

 that, with these last four compoxmds at concentrations just 

 below that required to inhibit germination, growth takes 

 the form of swollen bodies which tend to give a lowir value tP 

 the ratio of surface to volume of the organism than that re- 

 sulting from normal germination. This reaction to toxic 

 stimuli, at concentrations just below those required to in- 

 hibit growth, occurs commonly with all the salts here used. 

 That it is found with cane sugar, which is usually regarded 

 as non-toxic ( see True ) suggests that such reactions 

 may be brought about by high osmotic pressure as well as 

 by chemical stimulation in the true sense of this term. 

 This suggestion is in accord with the conclusions of Living- 

 ston (1 c. 18) who has shown that his form of Stigeclonium 

 will assume the palmella form in response either to a toxic 

 stimulus or to one of relatively high osmotic pressure. 

 Whether this effect of sugar, and similar effects produced 

 by high concentrations of calcium, magnesium and potassiiom 

 nitrates is really due, in the present instances, to osmotic 

 24. True, Rodney H. , The physiological effects of certain 

 plasmolyzing agents. Eot. Gaz. 26:4C7-416. 1898. 



