298 WaATTERSON: EFFECT OF CHEMICAL IRRITATION 
a slight advantage on the side of the irritated fungus. There is 
one exception to this, the fourth series, where the difference is 
unaccountably great, owing to an unusually large evolution of 
CO, from the stimulated culture. The increase in the amount 
of CO, given off is therefore but little greater than might naturally 
be expected from the increased respiratory surface due to the 
greater growth of the fungus. 
The second table shows the results of five experiments per- 
formed with the Pettenkofer apparatus ; the cultures, being grown 
at a lower temperature, 20-24° C., were allowed to run for a 
longer time: five, six, or seven days. In these, the figures for 
the irritated fungus represent the average of three cultures, grown 
under precisely similar conditions. Here too the ratios are very 
near one another. It is noticeable however that the difference, 
such as it is, is reversed in the second table, in all but one case, 
and the respiration of the normal grown in the Pettenkofer appa- 
ratus is therefore apparently a little greater, relatively, than that 
of the irritated fungus. The cause of this reversal of the ratios 
obtained by the two methods I have not been able to determine, 
but the difference is too slight to be of any importance. In 
Tables IX and X are given the same figures as in I and II, but 
the averages are found for the weights, CO,, and ratios of each set 
of series; that is, for the series obtained by the Kunstmann method 
(Table IX), the average ratio of weight to CO, for the normal is 
.98, for the stimulated culture is 1.18; for those in the Petten- 
kofer apparatus (Table X) the average is 1.16 for the control as 
against .94 for the stimulated fungus. 
Bearing these figures in mind, let us refer again to Ono’s ex- 
periments in determining the amount of oxalic acid produced by 
fungi during growth under stimulation. With all the irritants 
used, with the exception of NiSO,, he found a more or less marked 
decrease in the production of oxalic acid, a decrease shown (to 
quote some of his figures) * by the difference between 2.58 acid for 
every gram of dry weight of the normal, and 0.428 for the cul- 
ture to which has been added .003 per cent ZnSO,._ The duration 
of this experiment was twenty-seven days and the temperature 
16-20° C. Ono suggests three possible explanations for this de- 
* Ono, /. c. 174. 1900. 
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