474 
Kidd and West . — The Controlling 
breaking strain of the testa, due in all probability to secondary causes such 
as bacteria and acid accumulation. 
Changes in the Embryo. 
The experiments already described having thus given no definite 
indication of a change occurring in the seed-coats such as would be sufficient 
to account for secondary dormancy, it became necessary to consider the 
possibility of some change occurring in the embryo. 
To this end a comparison was made between the germination and 
growth of bare embryos removed from seeds showing secondary dormancy 
and bare embryos from normal untreated seeds respectively. 
In these experiments the seed-coats were removed with special care 
and the bare embryos were placed on damp filter-paper dipping into water 
in a closed vessel. The filter-paper was in some cases hung horizontally 
and in other cases supported in a slanting position on glass, the embryo 
being placed about i cm. above the water-level. When the tap roots 
develop they grow down into the water. In the case of the control with 
Table XVL 
Persistence of Secondary Dormancy after Removal of the Seed-coats. 
Experi- 
ment. 
Number 
of seeds 
used. 
Percentage of seeds p reviou ^ Ust of the 
Remarks. ungermmated after- seeds med in ' th J e se 
. 1 4 12 experiments, 
day. days. days. days. r 
Control experiment with 
No. 1 
10 
fully swollen uninhibited 0 
seeds. 
0 
0 
0 
21 days in inhibiting 
No. 2* 
8 
Kept in the dark at 20°C. 100 
5 ° 
0 
0 
gas-mixture. Set 20 
days after removal. 
19 days in inhibiting 
No. 3 
10 
„ „ 12*5° C. 100 
10 
0 
0 
gas - mixture. Set 3 
days after removal. 
No. 4 
10 
» >> )> 100 
40 
10 
10 
Ditto. 
17 days in inhibiting 
No. 5 f 
12 
» >> h 100 
50 
43 
8 
gas-mixture. Set 1 4 
days after removal. 
24 days in inhibiting 
No. 6 
20 
Kept in the light at 2o°C. 40 
5 
0 
0 
gas-mixture. Set 15 
days after removal. 
19 days in inhibiting 
No. 7 
7 
Kept in the dark at 12*5° C. 85 
15 
0 
0 
gas - mixture. Set 3 
days after removal. 
No. 8 
10 
)> >» tt 5 ° 
0 
0 
0 
Ditto. 
45 days in 28 % C 0 2 
2 
p 
VO 
20 
„ „ 16 0 C. 100 
50 
20 
20 
10 % oxygen. Set 
immediately after re- 
moval. 
* Cf. Plate XXIII, Fig. t, A and b. 
t Cf. Plate XXIII, Fig. 2, a and b. 
