274 Brown . — On the Germination and Growth of 
and in a refrigerator maintained at 3 0 . On examining these curves along 
the lines indicated above we have the following comparison : 
For Botrytis : 
A ir . 
10 % co 2 . 
20 °/ 0 co 2 . 
At 1 5 0 
3.4 (100) 
2.0 (59) 
1.0 (30) 
At 3 0 
3.4 (100) 
0.7 (21) 
0.0 (0) 
For Fus avium : 
At 1 5 0 
2*0 (TOO) 
1.8 (90) 
( 57 * 5 ) 
At 3 ° 
2.0 (lOO) 
0.82 (41) 
0.36 (18) 
Here in fact it is seen that in the case of Botrytis the low temperature 
combined with the depressing effect of 20 per cent. C 0 2 is effective in 
almost stopping growth over a period of 56 days. 
Similar curves were obtained for the growth of Alternaria and Monilia 
under the same set of conditions. 
Considerable attention has been paid throughout this work to the 
study of the ratio 
(growth in a given percentage of C 0 2 ) : (growth in air). 
The results arrived at may be stated as follows : 
1. In the case of any particular fungus and for a given temperature 
this ratio tends to increase as time goes on ; that is, the amount of 
retardation is greatest in the earliest phases of growth. For some fungi 
the ratio tends to reach a steady value, as is shown in the following table, 
which deals with the growth of Alternaria grossulariae. 
Table VII. 
Alternaria grossulariae. Groivth on Potato Agar. 
At 20°. 
2 days . 
3 days . 
5 days . 
7 days . 
8 days . 
Air 
i° 0 / 0 C0 2 
2G°/ 0 C 0 2 
1. 21 (100) 
i-oo (83) 
0.70 (58) 
2-10 (100) 
1.83 (88) 
1.38 (66) 
3.93 (100) 
3-65 ( 93 ) 
2.58 (66) 
6.05 -(i 00) 
5-i8 (86) 
3.78 (62) 
6.85 (100) 
6.15 (90) 
4.42 (64) 
At 5 0 . 
3 days . 
5 days . 
7 days . 
10 days . 
16 days . 
Air 
10 °/ 0 co 2 
20% co 2 
0.31 (100) 
0.09 (29) 
0.0 (0) 
1. 10 (100) 
0.48 (44) 
0* 10 (9) 
1.87 (100) 
0.96 (51) 
0.34 (18) 
3.14 (100) 
1-63 (52) 
o -73 (23) 
5.20 (ICO) 
3 'io ( 5 8 ^ 
1-45 (27) 
At both temperatures there is a tendency for the ratio of growth in 
C 0 2 to that in air to increase. That the ratio is smallest at the beginning 
is well shown in the experiment at 5 0 , and is obviously related to the fact 
that in the early stages there is a period during which the air cultures show 
fairly considerable growth while the C0 2 ones have not as yet germinated. 
In such a case the ratio of growth in C 0 2 to that in air is zero, but it 
begins to increase the moment the C 0 2 cultures spread beyond the limits 
of the original inoculum. The same effect takes place at the higher 
temperature, but in the present experiment the first measurement was made 
too late to show the rapid rise of the ratio in the early stages. At both 
temperatures the ratio tends to reach a steady value. This has been 
