Fungi at various Temperatures , &c. 269 
were analysed at each measurement, and in no case was there found a 
deviation of more than 0*5 per cent, from the concentration required. 
The incubation period and the rate of germination were found to vary 
to some extent with the different media employed, but the results obtained 
were of the same type for each medium and for each fungus. The following 
table gives the figures obtained for Penicillium on the two media, potato 
agar and apple gelatine : 
Table VI. 
Average Length of Germ~tiibe (in micrometer divisions). 
At 1 5 0 . 
12 hrs. 
16 hrs. 
20 hrs. 
23 hrs. 
36 hrs. 
Potato 
Air 
0.0 
0.36 
2.40 
4.72 
weft 
Agar. 
10 
% co 2 
0.0 
0-0 
0.32 
1*12 
12. 2 
. 20 
%co 2 
0*0 
0-0 
0-0 
+ 
4.84 
Apple 1 
Gplatinp 1 
(Air 
0-0 
0.70 
2.44 
5 * 12 
weft 
%C 0 2 
0-0 
+ 
0.44 
1. 10 
12.0 
1 
[20 
%C0 2 
0-0 
0-0 
+ 
0.26 
5.68 
A/ c 
0 
I 
2 
3 
4 
5 . 
6 
7 
8 
9 
Sil 5 
* 
day. 
days. 
days. 
days. 
days. 
days. 
days i 
days. 
days. 
Potato 
Agar 
(Air 
10 % co 2 
0.0 
0-0 
0.0 
0.0 
0.62 
o-o 
2.96 
0.0 
7.44 — 
0.82 2-96 
8.84 
z 
— 
( 20 %C 0 2 
0.0 
0.0 
0-0 
0-0 
0-0 
0*0 
0.22 
1.46 
3-84 
Apple 
Gelatine 
’Air 
10% CO, 
,20% co; 
0.0 
0.0 
0-0 
0-0 
0.0 
0-0 
009 
6 6^ 
to 
2.52 
0.0 
0-0 
7*52 — 
0-12 
0-0 0*0 
0.58 
2-14 
4.68 
The above figures illustrate clearly a feature of the germination of 
fungal spores — that from the moment germination has begun, growth 
proceeds at a constantly increasing rate (at any rate for some time). Thus 
if we plot the average germ-tube length as ordinate against the time as 
abscissa, the curve of growth is convex to the x-axis. 
The general quantitative effect of the two factors, low temperature and 
concentration of carbon dioxide, separately and combined, is perhaps better 
seen by comparing the time necessary for the average germ-tube to reach 
a given length in the different cases. Choosing a length = 5, and dealing 
with the germination tests on potato agar in the preceding table, we arrive 
at the following results : 
Average germ-tube = 5 is reached in : 
At 1 5 0 in Air c. 24 hrs. € 
,, 10 % C 0 2 24-36 hrs. 
„ 20 % C 0 2 36 hrs. 
At 5 0 in Air c. 4! days 
,, 1 o °/ o C 0 2 c. 6 j days 
„ 2o°/ 0 C 0 2 9 ( + ) days 
These figures illustrate the magnitude of the effect produced. Even 
in the case of this very resistant fungus and in abundant nutrient, the effect 
of a io° drop from ordinary temperature, combined with 10-20 per cent. C 0 2 , 
slows down the rate of growth in the early phases 6-9 times. 
