132 BOTANICAL GAZETTE [ aucust 
Two seedlings of Cucurbita Pepo were placed in each of the 
solutions of the strength shown in the following table: 
CUCURBITA PEPO. 
| 
‘ N N N N 
Acids. B00 | BI00 6400 T2500 
as 
ee ee CP ee 25°" rw 
ne! et Oe ONES IS ye |e ae es 3.25 * { 
HS Ree a NOG Sika Pr ease es 9. ae 
80, a Me IRS) ae ieee os 4.75": 6.5 3 
se ee eee 5.25% To 
0.4 24 ye ee eo $.e. ee 
HB Per eA OUTS a 4.5250 5.7 
sf SS Oe ens errr 2.35 i ai 
Boe lL 
Seedlings were set first in the veny and sout solutions and 
after the first twenty-four hours no growth had taken place 
replaced 
the root tips were soft and flabby; they were, however, 
in the solutions and allowed to stand for another twenty-four 
hours. Atthe end of the forty-eight hours no additional growth 
had occurred. In the givy and ,,45,5 solutions the growth 
considerable for both the first and second twenty-four how 
Then the strength of solution necessary to inhibit the growth 
— 33 Which is less than in the case of Pisum sativum seedlings : 
but more than in the case of Zea Mais seedlings. : 
The relative sensibility to the acid poisons then is a 
1. Pisum sativum, seedlings killed by ,,\,y solution. 
2. Zea Mais, seedlings killed by ,¥,, solution. 
3- Cucurbita Pepo, seedlings killed by , 4, solution. 
follows: 
Before discussing the results of the experiments with 
acids, a short statement in regard to the so-called theae 
electrolytic dissociation will be necessary. The theory ie i 
lished by Arrhenius‘ in 1887 and amounts practically ee 
Aqueous solutions of acids, bases, or salts are, to 4 me 
less extent, broken up or dissociated into part-molecules, - 
called zons. It is not necessary to mention here the facts or 
confirm this theory, but it suffices to say that it now stands OP 
* Zeitschrift fiir Physikalische Chemie 1: 631. 
