INORGANIC SALTS TO MONILIA SITOPHILA 281 
striking way the low resistance of peptone media and indicates 
that Monilia is actually able to endure higher concentrations of 
these poisonous substances when it is growing in peptone media 
than when it is in any of the other media which have been used. 
The table also suggests the probability that the susceptibility of 
the [fungus to the same kind of ions varies according to the 
medium in which it is growing. 
In an attempt to further elucidate the nature of the toxic 
action of the various salts on Monilia, I have also attacked the 
problem from the standpoint of the hypothesis that failure of the 
spores to germinate in a medium containing less than the lethal 
dose of a toxic substance is due to the inability of the protoplast 
to absorb sufficient water. Careful observation of the appearance 
and behavior of spores in toxic media has led to the belief that the 
retarding action of a toxic salt on germination and growth is the 
result of its influence on the ability of the cells to take up water. 
As has already been stated, the highest concentration of a salt 
in which Monilia spores show germination after three days, has 
been designated the limit concentration for that medium. It is 
recognized that this is an arbitrary standard. The limit concen- 
trations given in the above tables hold only in the case of an incu- 
bation period of three days. Germination will take place in 
concentrations which are greater than this limit concentration, 
provided the spores are left in the medium for a longer period of 
time. 
Spores placed in a medium in which the toxic substance is 
slightly more dilute than the limit concentration, germinate and 
produce mycelia. The rate of growth in such a medium is much 
Slower than in a non-toxic medium. The most obvious char- 
acteristic of a poisoned culture is the long incubation period and the 
slow rate of growth. The effect of potassium chloride on the time 
of germination of spores of Monilia on a potato medium (thirty- 
five per cent. potato cubes) is shown by Table XIV. 
While growth becomes visible in twenty-one hours in a medium 
containing potassium chloride at a concentration of .62 molar, it 
takes thirty-four hours when the concentration is 1.26 molar 
and fifty-five hours when the concentration is 1.9 molar. This 
€xperiment illustrates the behavior of the fungus in media which 
are toxic but which do not entirely inhibit growth. 
