1 62 Gardner — Studies on Grozvth and Cell 



His work, however, is not precisely in the same hne as that of 

 the writer, for his experiments were performed to show that 

 the toxic action of solutions of electrolytes is due to the action 

 of the ions present. 



Mr. T. D. Heald, in a paper entitled "Toxic Effect of Acids 

 and Salts upon Plants," ^ has shown the effect of various 

 chemical solutions on seedlings. He finds that the relative 

 sensitivity' to acid poisons is as follows : 



N 

 Fisum sativum seedlings were killed in solution ^^ 



ZeaMays " " " " " ^ 



N 

 Ciicurbita Pepo " " " " " 3200 



When expressed in the form of per cent the extremely 

 small amount of acid necessary to kill Pisnm sativum seedlings 

 is even more striking, and may be expressed as follows : 



HCl 0.00056 per cent. 



H^SO^ 0.00076 per cent. 



HNO3 0.00098 per cent. 



HBr 0.00126 per cent. 



He further experimented with a long series of salts of 

 Nickel, Cobalt, Copper, Mercury, Gold, etc., and showed the 

 toxic action to be due to the ions into which the substances 

 split up, in great dilution. 



The writer's experiments were performed with solutions of 

 HCl, NaCl, (NH4)2C03, of strengths varying from two to one 

 one-hundredth per cent. Seedlings of the pea, bean and corn 

 were used. These were placed in pots filled with thoroughly 

 washed asbestos, and the asbestos was kept moist with the 

 respective solutions. Asbestos was used in preference to saw- 

 dust to prevent any fermentation or chemical reaction, which 

 the latter when in contact with the solutions might induce. 



The growth of the root, i. e., the increase in length, was 

 measured daily. Every set of experiments includes a control 

 in which ordinary water is used, so that Avith this as a stand- 



2Bot. Gazette, vol. 22, 1896. 



