Fungi at various Temperatures , &c. 275 
reached at the higher temperature by about the fifth day; at the lower 
temperature it has not been quite reached by the sixteenth day, though 
inspection of the table shows that the daily increase in the ratio is getting 
less and less. At the higher temperature the ratios of growth in 30 per cent. 
C 0 2 : growth in ic per cent. C 0 2 : growth in air, tend to reach the limiting 
values 65 : 85-90: 100, whereas the corresponding ratios for growth at 5 0 
are in the neighbourhood of 30 : 60 : 100. 
These tables again illustrate the effect of a lowering of temperature 
on the retardation of growth produced by a given concentration of carbon 
dioxide. 
In the case of some fungi, and especially when they are sown on 
certain media, the ratio of growth in C 0 2 to that in air goes on increasing 
with time without showing any tendency to reach a limiting value, at least 
within the limits of size to which the colonies have been studied. In such 
cases as these the growth of colonies in the C 0 2 concentrations finally 
exceeds that in ordinary air, especially at higher temperatures. The 
following table dealing with the growth of Fusarium will illustrate this 
point : 
Table VIII. 
Fusarium . Growth on Potato Agar. 
At i 5 °. 
3 days. 
5 days. 
7 days. 
8 days. 
Air 
1 0 °/ 0 co 2 
20 °/ 0 C0 2 
1.23 (100) 
i-i (85) 
°-95 ( 73 ) 
2-23 (100) 
2-4 (108) 
2.1 (94) 
2.98 (100) 
3*5 (”8) 
3-3 Cm) 
3-3 (100) 
4.04 (12 E) 
3*8 (115) 
At 5 0 . 
7 days. 
14 days. 
21 days. 
35 days. 
Air 
10 0 / o COo 
2o°/ 0 co; 
0-4 (100) 
or (25) 
o-o (0) 
i-6 (100) 
0-8 (50) 
0-05 ( 3 ) 
2.2 (100) 
!'3 ( 59 ) 
o’- 1 8 (8) 
3.85 (100) 
2-5 (65) 
0.7 (18) 
The present case brings out best of all the effect of temperature on 
the retarding action of carbon dioxide. Corresponding to a colony diameter 
of 3*85 at the lower temperature, there is very considerable retardation 
in the C 0 2 atmospheres, whereas at the higher temperature the colonies 
in 10 per cent, and 20 per cent. C 0 2 are distinctly ahead of the colonies in 
air for some time before the latter reach that value. It is not proposed to 
discuss this effect here, as it will be dealt with more fully in a later paper, 
but it may be stated that it is related to the marked ‘ staling ’ which takes 
place in the air cultures. The main feature of ‘ staling ’ in the present case 
is the development of alkalinity by the fungus, and this is partly counteracted 
by the action of carbon dioxide. Hence while the air cultures at 15° 
become progressively slower in growth, the C 0 2 cultures keep up a steady 
rate of growth for a longer time, with the result that the initial retarda- 
tion produced by carbon dioxide is sooner or later converted into an 
acceleration. 
As will be shown more fully in a subsequent paper, the particular 
