1899] TOXIC EFFECT OF DELETERIOUS AGENTS 393 
which inhibited the spores of Aspergillus failed to kill them was 
nowhere else paralleled with this form and but once surpassed by 
Penicillium. 
Cobaltous sulfate stands in second place in this group as an 
inhibiting agent, but, as will be seen, it is relatively much more 
powerful as a disinfectant. Penicillium, however, showed its 
usual high powers of resistance in this respect. Inhibited by 
n nu 
> was required to kill. 
Ferrous sulfate-—Iron, a necessary element for the nutrition 
of the molds (Molisch, ’94) in common with all other plants, in 
excess proves to be a very strongly toxic agent, surpassing in 
this respect that king of modern fungicides, copper. With the 
exception of nickel as noted above, iron showed a greater differ- 
ence between the average concentration required to inhibit the 
spores and the concentration required to kill than any other 
agent. Botrytis, as usual, showed less variation in this respect 
than the other forms, but even with it one eighth the fatal con- 
fentration inhibited germination. (CEdocephalum showed the 
§teatest resistance to this agent both as regards inhibition of 
sermination and killing of the spores. This was the only 
agent with which it had a higher specific resistance than any 
other form, 
Copper sulfate and nitrate.—These salts proved to be quite 
Similar in toxic properties, as may be noticed by a glance at the 
. diagrams, p. 312. The nitrate, however, is much more highly 
| ionized at the critical concentrations ; hence we judge that the 
| “N-ionized molecule CuSO, has a toxic value not greatly differ- 
it from ionic +Cut. : 
Hn 
Penicillium, although inhibited by se Cu(NO,), and = 
CuSO, required a ” concentration in both cases to kill the spores. 
: This certainly shows great resistance to these agents as compared 
_ With the other molds. It, however, appears insignificant when con- 
. n 
- tasted with many of the results gotten by other workers. [53 
