462 
Kidd and West . — The Controlling 
Table V. 
Effect of various Partial Pressures of Carbon Dioxide ( 
present) on the Production of Secondary Dormancy 
alba. 
10 per cent. Oxygen 
in Seeds of Brassica 
£ 
8 
1 
$ 
o 
v 3 
a 
■SO 
< a 
gjs ^ 
a ^ .H 
•| | 1 
II 
•a . 
^ § 
. 8*5 
Germination after removal 
of the seeds in air. 
Number of days. 
3 4 5 6 7 10 
Temperature during inhibition period, I3°C. 
* Show injury to the primary root. 
^ & 
rli 
50 
5 % 
21 
36 
H 
1 
6 
7 
9 
9 
9 
9 
3 
50 
10% 
21 
3 * 
45 
0 
5 
9 
10 
10 
11 
12 
0 
73 % 
50 
i 5 % 
21 
5 * 
45 
0 
1 
3 
4 
8 
10 
16 
1 
62% 
50 
25% 
21 
0 
50 
0 
6 
10 
15 
17 
19 
19 
3 
56 % 
50 
50% 
21 
0 
50 
0 
10 
13 
18 
18 
21 
25 
0 
50% 
50 
7 ° % 
21 
0 
50 
0 
io 
24 
30 
36 
37 
4 i 
7 
4 % 
50 
90% 
21 
0 
5 ° 
0 
12 
J 9 
27 
30 
32 
40 
9 
2% 
■§:§ 
^ ^ ^ 
1-5; 8 ^75 **■ 
^ 0 
a s 3 r 1 •kj 
55 ^ a v-S 
S g a h 
^ g 
« % 
2% 
4% 
10 I 
20 % 
7°% 
88 % 
In the series of experiments with no oxygen present (Table VI) no 
secondary dormancy was obtained. The main fact emerging is that 
secondary dormancy cannot be produced by the exposure of seeds to 
carbon dioxide alone in any concentration. This result is in accordance 
with the experiments described in the previous section. 
Table VI. 
Effect of various Partial Pressures of Carbon Dioxide (no Oxygen present) on 
the Production of Secondary Dormancy in Seeds of Brassica alba. 
*a 
-3 8 
8 2 
■ 2*0 
s a 
■IS 
So 
.so 
'K CJ 
a a 
^ a 
5 s 
. 
g 
Germination after removal 
of the seeds to air. 
Days. 
1 * 
f *1 
£ 
o, 
30 
0% 
21 
0 
30 
6 
13 
15 
15 
15 
15 
15 
16 
3o 
25% 
15 
0 
30 
0 
5 
13 
19 
2 1 
24 
24 
30 
5°% 
15 
0 
30 
0 
6 
24 
26 
26 
26 
27 
30 
0% 
30 
80% 
J 5 
0 
30 
0 
2 
4 
8 
11 
13 
15 
15 
°% : 
30 
IO °% 
21 
0 
30 
0 
0 
0 
0 
1 
2 
3 
5 
°% : 
Temperature during inhibition period, I3°C. 
S ^5 i 
~ 
^ ^ a 1 
gM 
^ £ 
a ^ 
* All seeds still ungerminated after 10 days in air were either dead or so badly injured with 
regard to the radicle that they finally decayed. 
Marked injury to the radicle occurs in these experiments in the absence 
of oxygen, and a correlation between subsequent germination and injury to 
the radicle thus appears again. 
