eee eee 
1902] TOXIC PROPERTIES OF COPPER COMPOUNDS 29 
markedly in their capacity to resist poisons and other unfavor- 
able conditions. 
I would emphasize the importance of considering the fort 
of inhibition of germination rather than the death point in consult- 
ing these results. The former can be determined with ease and 
absolute certainty by direct observation under the microscope, 
the latter only by transferring the spores to a fresh culture free 
as possible from the deleterious agent, and determining their 
success or failure to germinate under these conditions. The 
unavoidable source of error here is the transference of more or 
less of the copper compound with the spores. . This quantity is 
doubtless often sufficient to prevent. the germination of spores 
which although greatly reduced in vitality may be still alive. 
The general result of such transfers made at varying intervals 
from twenty-four hours to ten days indicated that if the germi- 
nation of the spores be inhibited by a concentration of a copper 
salt, it was merely. a question of time when they would be 
killed. Thus if a certain concentration inhibited the germina- 
tion of a certain spore, possibly a solution of four times this 
concentration would fail to sterilize the culture in twenty-four 
hours, yet if left for some days the points of inhibition and 
death would finally coincide. The length of time necessary to 
bring this about would naturally vary with the varying specific 
characteristics of the spores of the different species. 
The medium used for the cultures, the results of which 
are given in fig. 7, was a decoction of sugar beet. The root, 
sliced thin, in the proportion of 450 per liter, was heated in an 
autoclave for an hour at 120° C., under a pressure of one atmos- 
phere. The decoction was then filtered and poured into flasks 
and thoroughly sterilized. This medium was selected for the 
comparative tests as giving the best results with the greatest 
number of the fungi used. The other vegetable decoctions 
were prepared in essentially the same manner. 
Stock solutions of the various copper compounds were pre- 
pared by a responsible chemist. A xormal solution of a copper 
compound means in this paper the number of grams of the salt 
