1896 | TOXIC EFFECT OF ACIDS AND SALTS UPON PLANTS 147 
The results of the experiments for the seedlings of Zea Mais 
are given in the preceding table. 
For the seedlings of Zea Mais it was only necessary to use 
three dilutions. Inthe first two of these the roots showed a 
slight growth during the first twenty-four hours, but no further 
growth was shown by the second measurement. In the 5)y599_ 
equiv. solution the growth continued for the entire period, so 
that here, as in the case of Pisum sativum experiments, the kill- 
ing point is shown to be the + s';ya equiv. solution. Here also 
the roots which were killed remained quite rigid. 
In Ag,SO, the dissociation will be into two Ag* ions and 
“SOZ ions. The AgNO, will dissociate to form Ag* ions 
and “NO; ions. It has already been shown in several cases 
that the ~SO; ions and NO; ions are without any toxic 
action. Now since dissociation is practically complete in the 
dilutions used, only the ions are to be considered, and the non- 
POisonous character of the electro-negative ions leaves the Ag* 
ions to produce the toxic effect. 
The extremely small amount of ionic silver necessary to kill 
the root may be expressed as follows: 
Both seedlings killed by soscsy 69-1 part Ag to 948,148 
H,0. According to the above the silver ion is somewhat more 
Poisonous than the copper ion. 
g. MERCURY. 
Experiments were performed with the seedlings of Pisum 
sativum and Zea Mais and a single mercury salt, HgCl,. The. 
results of these experiments are given in the following table : 
CORROSIVE SUBLIMATE. 
————=—=_-—_ 
toe Zs Be es 
He Cl, TTSVO =5b 00 Srs00 L0sF00 ZOTSOO | £09600 
mol, mol. mol. mol. mol, mol. 
Pisum 
Sativum ) St 24 Hye... gmm 2.25™™ | 3.75™™ 6.75™ 4.5 
oe Ge fete eee su) Jae ae 
Zea Mais i) Ist 24 hrs gmm PP eps 19°" 145°" ae 
(2d 2ghrsi ... | 10 28 10.5 * 
ER ae ee ah eT 
