396 BOTANICAL GAZETTE [ DECEMBER 
All of the copper salts agree closely in toxic action. 
Between potassium chromate and bichromate there is a 
remarkable variance; the bichromate has twice the effect upon 
Botrytis, thirty-two times the effect upon Macrosporium and 
sixteen times upon Uromyces that the chromate does. 
In all the cases considered so far, it will be noticed that with 
the exception of Penicillium, Uromyces will withstand as great or 
greater strength than any of the other fungi tried. With NaCl 
we have a case, however, in which the Macrosporium survives 
even a greater strength than the Uromyces. The same anomaly 
is observed with HCl and H,SO, upon these fungi. So it seems 
that although a fungus may, generally speaking, be more resistant 
to the action of salts or acids than other fungi are, there may be 
some particular substances which will affect this fungus at less 
strength than is required for the other and usually weaker fungus. 
This fact is especially important in the application of fungicides, 
in that a fungicide which is most effective for one fungus is not 
necessarily so for all fungi. It may also be noticed that although 
Uromyces is generally more resistant than Botrytis and Macro-_ 
sporium, Uromyces is the most susceptible to the action of NaCl. 
The hydroxids KOH, NaOH, and NH,OH gave quite uni- 
form results, and show a low toxic power. In the case of the 
hanging drop this might partially be explained by the neutrali- 
zation by CO,; but, substantiated as it is by parallel experi- 
ments in gross culture with a Penicillium, the fact must be 
accepted that the hydroxids are of low toxic action on these 
fungi. 
Potassium permanganate is of very low toxic power, but is of 
peculiar interest in that it has the power of coloring the uredo- 
spores a dense black, while the teleutospores were but slightly if 
at all darkened. The other records made in table XVII show 
that the solution is practically non-toxic. 3 
An inspection of this table will show that, of the five fungt 
tried, Penicillium is usually more resistant than any of the others. 
This is rather to be explained by the means of culture than by 
any structural or selective difference in the fungi themselves. 
