318 BOTANICAL GAZETTE [NOVEMBER 
Sulfuric acid, % H,SO,; 61, 205,589. As will be observed, 
of this agent is based on the half molecule in order to make it 
strictly comparable with the other acids, the others being all 
monobasic. 
aE <n 
H,SO, becomes ionized first into H and HSO,, ions, but as 
fe - 
dilution increases the HSO, ion further breaks up into H and 
~SO,. The ionization of H,SO, at the average inhibiting point is 
about 62 per cent. only (Kohlrausch ’85). Each 100 molecules, 
then at this concentration breaks up into approximately 124 H, 
76 HSO, and 24 SO, ions. This solution having a greater toxic 
value than a similar concentration of ionic Hi and the anion being 
practically non-toxic, the excess of toxic properties must be due 
to the partially ionized group HSO,. By referring to table I it 
will be seen that the toxic value if this anion is approximately 
1.3 in terms of ionic H. 
In this as in the other mineral acids, Sterigmatocystis proved 
the most resistant, - being necessary to kill. Botrytis was the 
most easily killed, ~ being fatal. CEdocephalum, although requit- 
ing concentration to kill the spores, was considerably injured 
By so greatly injured by S , and produced a very light yeast- 
like mycelium in Sn which on the third day practically ceased 
growing. On the whole, H 250, retarded germination less ah 
HCl and HNO,. ac 
Acetic acid, ‘CH ,COOH; 25.6, 83, 314. This acid at 
inhibiting point, - — is but 2 per cent. ionized (Koh '85): 
t as 
The toxic value of oF anion was found to be about qs 1, H, ne < 
so small a proportion of the acid is ionized the influence ° 
his acid are 
anion may be disregarded. The toxic properties of t 
