28 BOTANICAL GAZETTE [JANUARY 
have as nearly uniform a quantity of spores in the various cul- 
tures compared as possible. It is equally important to avoid 
bunches of spores in making the inoculation. Oversight in 
regard to either of these points is bound to result in more: 
less erratic and unreliable results. This is due to the fact that 
a toxic agent like copper, which effects the death of the spores by 
uniting with and precipitating the protoplasm, is itself also pre- 
cipitated in the process and can no longer exert a deleterio 
influence. This precipitation process is naturally a strictly quan- 
titative matter, and the amount of copper sufficient to sterilize 
culture containing fifty spores may prove entirely inadequa 
were the number of spores quadrupled or even doubled. When 
bunches of spores are present the effect is still more mischievous. 
These bunches are relatively slowly penetrated by the copper- 
containing solution. Should the bunch contain air, as is usually 
the case, the process of penetration of the copper to the inner- 
most spores is still further retarded. In the meantime such 
spores as are floating singly are quickly killed, precipitatit 
their share of the copper, and it may be that long before the 
solution has fully penetrated the bunch it may have lost the 
greater part of its soluble copper and may be no longer able 
kill the remaining spores. These may then germinate and gro 
almost as well as if no poison had been present. The difficulty 
was entirely overcome by soaking the spores for a longer OF @ 
shorter time in sterile distilled water with an occasional shakin 
In some cases this soaking may be continued with advantage f 
days, in which case it is well to keep them at a low temperat 
to prevent germination. In all cases it was advisable to inoc 
late from a mixture of spores in water, a uniform inocula 
being approximated in that way without great difficulty. 
equally important to have the culture drop, of as uniform a 
as possible. Absolute precision in these matters, however 
impossible, and the reader is reminded that slight variations | 
all cultures are to be expected. Indeed, as has been often su! 
gested, spores taken from the same sporangium and placed 19 
the same culture under absolutely similar conditions vary V 
