162 Gardner—Studies on Growth and Cell 
His work, however, is not precisely in the same line 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 
Pisum sativum seedlings were killed in solution —3 
N 
/ ¢ TEND 
Zea Mays rs ek ee Te 1600 
Cucurbita Pepo fe eer aU 00 
When expressed in the form of per cent the extremely 
small amount of acid necessary to kill Pzswm sativum seedlings 
is even more striking, and may be expressed as follows : 
ECL aes ok eo Beep tie aug 1 ae . . 0.00056 per cent. 
ELSON a eal vara. sate Ramla tants 0.00076 per cent. 
ELINOR et YX eulken a date ee secs ercneaee 0.00008 per cent. 
lab? OA etc s Aa aa Lon cncerae © 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, (NH,),CO, 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, z. ¢., the increase in length, was 
measured daily. Every set of experiments includes a control 
in which ordinary water is used, so that with this as a stand- 
2 Bot. Gazette, vol. 22, 1896. 
