134 BOTANICAL GAZETTE [ AUGUST 
In regard to the relation of these results to the theory of 
dissociation, Kahlenberg and True® have demonstrated quite 
clearly in their work that it is the H* ion which produces the 
toxic effect. HCI will form H* ions and Cl- ions; H,S0, 
will dissociate first into H* and HSOj, but the final product 
will be two H* ions and ~SO; ions; HNO, splits to form H* 
ions and NO; ions; HBr will dissociate to form H* ions and 
Br* ions. As has been before stated, the more dilute the 
solution, the more complete the dissociation, but with the dilu- 
tions used for the acids, dissociation would be practically com- 
plete, so that we need not take into consideration anything but 
the H* ions and the electro-negative ions. Take for example 
NaCl, which will dissociate as Na+ and Cl~ ions. Now Na 
at the dilution at which the HCl was effective is practically 
without effect; the Cl- ions must then be considered as nom 
poisonous in the HCl, since both HCl and NaCl contain 
ions. Now if the Cl- ions are without any toxic effect at this 
dilution it is plain that the poisonous effect must be due to the 
H* ions, 
The H,SO, may be considered in the same way. If a: plant 
be subjected to an equally concentrated solution of K,S0y 
which is one of the compounds from which plants quite comm: 
monly obtain their potassium, it would be entirely unharmed # 
that dilution. The K,SO, would dissociate to form Sc os 
and SO; ions, and since K,SO, and H,SO, solutions ae 
SOZ ions in common it is evident that the SO; ions 0 the 
H,SO, are non-poisonous. This then leaves only the H_* ions t 
produce the toxic effect. The non-poisonous character of Be 
Ba eas a be shown by the action of other sulfates; “7 : 
eee: gsO, and Na,SO,. Again: sulfur is a constant se 
stituent of proteid substances, and is absorbed by all plants 
oe Daou so that plants are constantly sub) ee - 
H.SO. saleuan areas: The solutions were so woo fs 
other acids th : Diet tee ere —— pee d only Ah 
» that is, a normal solution of H,SO, containe ; 
° Bor. Gaz. 22:8. 1896, 
