284 KUNKEL: FACTORS INFLUENCING TOXICITY OF 
potassium chloride solution be suspended in an oiled paper bag 
above a young culture, it checks the growth of the mycelium to a 
remarkable extent. The less concentrated the solution in the 
paper bag, the greater will be the mycelial growth in the culture 
above which it is suspended. Drying the air by placing small 
amounts of calcium chloride over the cultures gives still more 
striking results. The mycelium can be kept from rising more 
than a few millimeters above the surface of the medium. Table 
XV shows the effect of suspending potassium chloride solutions 
of different concentrations over cultures kept under conditions 
that were otherwise identical. The bags containing the solutions 
were placed in the bottles at the time the inoculations were made. ° 
TABLE XV 
INFLUENCE OF HUMIDITY ON THE GROWTH OF Monilia 
Solution Suspended Above Culture Height of Mycelium After 32 Hours 
c.c. of 4.0 molar KCl solution. 10 '¢ 
tie. 347 Pa ae 
§ Cet Rae OBE et! e62! 
oA seman ois Pa eta (capa ad ro ean 
jaf oe craeglcuiene - Caeueaae ee a Ss ESTES ce aes 
5 ¢.c. “ distilled water 107° 
Fic. 1 shows the six cultures referred to in Table XV. The 
photograph was taken several hours after obtaining the measure- 
ments used in the table. The culture that made the least growth 
is the one above which was suspended five cubic centimeters of 
four molar potassium chloride solution. Distilled water was 
suspended over the culture that made the greatest amount of 
growth. As the rate of loss of water by the mycelium is increased 
the rate of growth is correspondingly decreased. By suspending 
one gram of anhydrous calcium chloride over alternate cultures 
(Fic. 2) the influence of vapor pressure on rate of growth is still 
more strikingly shown. The amount of water taken up by the 
calcium chloride, however, is very small. 
In order to determine the amount of water taken up by calcium 
chloride suspended over cultures of Monilia when it causes such 
variations in growth as are to be noted in Fic. 2, bags were 
weighed before and after being suspended over cultures. The 
difference in weight gives the amount of water taken up by the 
