INORGANIC SALTS TO MONILIA SITOPHILA 283 
centration inhibits germination, it does not kill the spores, even 
after considerable periods of time. When the concentration is 
still further increased the water holding power of the spores 
becomes less and plasmolysis results. 
If as is here assumed the rate of growth of the fungus in a toxic 
medium depends on.-its rate of water absorption, then any means 
by which the water content of the mycelium could be lessened 
should also decrease the rate of growth. If, for example, Monilia 
be placed in a dry atmosphere where the loss of water by the 
aerial part of the mycelium would be great, the rate of growth 
should be correspondingly decreased. The following experiments 
show the effect of a dry atmosphere on the rate of growth of the 
fungus mycelium. 
The media used in this work consisted of cubes of potato to 
which was added enough water to fill the bottom of the culture 
vessel to depth of about one half of a centimeter. On such a 
substratum Monilia makes very abundant growth. The cultures 
were incubated at a temperature of 29° C. This is one degree 
below the temperature most favorable for its growth (see Went, 
34). Since the effect of drying the atmosphere over cultures of 
Monilia varies somewhat with the age of the culture at the time 
the drying agent is used, a few remarks regarding the appearance 
of the fungus at different stages in its development seem desirable 
at this point. 
Under the conditions outlined above, growth first becomes 
visible to the naked eye after an incubation period of from nine to 
ten hours. During the next fifteen hours the mycelium grows so 
rapidly that it almost hides the surface of the potato cubes. _ In the 
next seven hours the fungus makes still more rapid growth, rising 
from five to ten centimeters above the culture medium. This is 
followed by a period of about six hours, during which there is 
little visible change. When the ctltures are approximately forty 
hours old they begin to take on a beautiful pink color and during 
the next hour spore formation begins. 
If the vapor pressure above cultures that are more than thirty 
hours old is unduly lowered, the mycelium withers and fails to 
Produce spores. An entirely different result is obtained in the 
Case of young cultures. If five cubic centimeters of a four molar 
