1899] TOXIC EFFECT OF DELETERIOUS AGENTS 389 
silver, while Aspergillus and Botrytis were more susceptible to 
mercury. The fifth form, Sterigmatocystis, had an equal resist- 
ance to both. The extraordinarily small quantity of mercury 
required to kill Botrytis, however, left the honors with mercury 
as the more deadly agent. 
A very striking contrast in specific resistances is afforded by 
Botrytis and Penicillium in solutions of these agents. One six- 
teenth the amount of HgCl, necessary to kill Penicillium was 
fatal to Botrytis. With AgNO, one fourth the concentration 
_ fequired to kill Botrytis was fatal to Penicillium. Or, putting it 
another way, AgNO, has eight times the toxic value of HgCl, 
toward Penicillium, while the exact converse is true with Botrytis, 
HgCl, being eight times as effective as AgNO, to this form. 
The low resistance of Penicillium to silver is quite striking, 5 
Proving fatal. In one other case only (H,O,) did Penicillium 
show a lower resistance than Botrytis. 
Toward splenic fever bacteria gold is the only other metal 
‘omparable in toxic properties with mercury and silver (Daven- 
port '97, p. 14). Toward phanerogams silver is much more 
to 
a 
a 
i Zea, and ———— 
see being fatal to 204800 
Lupinus (Heald ’96, p. 152). At the concentrations used the 
AgNO, would be practically entirely ionized (Kohlrausch, ’85). 
Cadmium nitrate, Cd(NO,) 4; 0.075, 6.7, 24. Ranking closely 
With silver as a poison for the higher plants, cadmium proves 
tobe very highly toxic to the mold fungi. Perhaps the most 
Marked feature in the cultures with cadmium was the very wide 
ange between the killing point and the point where develop- 
ment was only noticeably injured. It will be noticed that the 
: Tatio of its coefficient of injury to that of HgCl, is less than 
_'Lwhile the ratio between their death points is 75:1. A sec 
ond str iking feature of the toxicity of cadmium is the great varia- 
toxic than mercury, 
‘ * ‘ = 
Fon in the specific resistances of the different forms. 4096 
Moved fatal to Botrytis, but — was required to kill Sterig- 
: 32 
