324 BOTANICAL GAZETTE [NOVEMBER 
Ascaris resists a 3 per cent. solution for 75 minutes. A myria- 
pod (Fontaria) excretes HCN when irritated! The accumula- 
tion of many such data has led to the general acceptance of the 
theory that HCN acts chiefly or wholly upon the aldehydes of 
the nerve centers (Loew ’93). This is no doubt quite satisfac- 
tory from the point of view of the animal physiologist, but it 
leaves us without any explanation for its violent toxic properties 
toward plants, which have no nerve centers. 
Little work seems to have been done with it on plants. 
Kahlenberg and True (’96) found that toward Lupinus it had 
a . 
double the toxic value of ionic H proving fatal. To the 
Li 
’ 6400 
molds, however, it is relatively a much more powerful agent, 
415 : : 
having 76.6 times the value of H, thus ranking as one of their 
most fatal poisons. The data on the ionization of this acid are 
meager. At as it gives about one sixteenth the electrical con 
ductivity of acetic acid at the same concentration (Ostwald 85). 
From this we would judge that the ionization is practically zero 
at the concentrations with which we have to deal. 
The value of the CN ion was determined by means of the 
potassium salt, which is quite highly ionized (Kohlrausch 79): 
Were 
It was found to be approximately 8H _ for the molds. 
a toxic 
HCN fully ionized we would expect its solutions to have 
value of about oF. The fact that the practically un-fonit® 
solutions with which we deal have a value of over eight Humes - 
calculated for the entirely ionized acid tells for the extreme!y 
toxic influence of the un-ionized molecule, HCN. a 
Aspergillus showed a high specific resistance to this age™ 
= being necessary to kill all the spores. CEdocephalum 4 
"inhibited by 3943’ 
32768’ 
particularly sensitive, being injured by 
and killed by ne 
i of the 
In table I the toxic values of the un-ionized molecules 
