282 KUNKEL: FACTORS INFLUENCING TOXICITY OF 
TABLE XIV 
THE EFFECT OF POTASSIUM CHLORIDE ON RATE OF GROWTH 
Concentrations of KCl | Incubation Period Concentrations of KCI | Incubation Period 
0.62 molar. | 21 hours. 1.42 molar. 36 hours. 
o4000" at Peo | a des 
0.78 se 23 é 1.58 “6 38 ee 
0.86 ae | 25 ee 1.66 é | 40 ee 
0.94 ss 27 “ae 1.74 “es 42 “ee 
I O2 oe 29 é r.82 oe | 44 oe 
1.10 ‘ | 31 ‘ 1.90 “ce ue se 
1.78 oe | 32.5 ee 1.08 ae 59 ee 
1.26 “e 34 “ 2.06 ‘ 63 ‘ 
E34. °" | i <i ey eae No germination after 
| 20 days. 
If now we study the condition of the spores in media that 
entirely inhibit germination, we obtain some interesting data. 
The spores will remain viable for two weeks or longer in the pres- 
ence of so toxic a substance as mercuric chloride, provided the 
concentration is slightly below that which causes plasmolysis. 
Some spores which had been kept for two weeks on a starch 
medium containing mercuric chloride at a concentration of .00005 
molar germinated when transferred to potato agar. This shows 
that although the spores do not germinate in such a toxic medium, 
they are not much injured by it. The toxic substances which I 
have used cause serious injury to the spores, only when they are 
concentrated enough to bring about plasmolysis. At concentra- 
tions less than this, the spores do not germinate but they remain 
alive for a long time. At still lower concentrations they not 
only remain alive but germinate and make a slow growth. 
This slow growth in media containing approximately limit 
concentrations of toxic substances seems to me strong evidence 
that although the poison is not present in sufficient quantities to 
cause plasmolysis, it nevertheless hinders the absorption of water 
by the spores and in this way inhibits their growth. This assump- 
tion seems fully in accord with the facts above noted. As the 
concentration of the toxic substance is increased, the ability of 
the protoplasm to absorb water becomes less and less and the time 
required for germination longer and longer. A concentration is 
finally reached at which the spores are no longer able to absorb 
any water from the surrounding medium. Although this con- 
