443 
Relation to the Germination of Immature Seed. 
the seed-coat, attributing to them a role in causing dormancy similar to that 
which we are here attributing to the respiratory activity of the living testa. 
Experiments with Pisum sativum. 
The results of certain experiments with immature seeds of Pisum 
sativum are recorded in Table V, and appear to be essentially similar to 
those obtained with Brassica alba. 
Table V. 
A. 
B. 
C. -I 
D. 
E. 
Germination of seeds and bare embryos of Pisum sativum at different 
stages of maturity. 
Lot I. Twenty immature seeds. These had attained their full size 
(the funicle comes away with the pea when taken from the pod). 
Lot II. Twenty bare embryos from similar seeds. 
Lot I. Twenty less immature seeds (peas break from the funicle when 
taken from the pod). 
Lot II. Twenty bare embryos from similar seeds. 
(Lot I. Twenty seeds picked ten days later. 
(Lot II. Twenty bare embryos from similar seeds. 
Twenty seeds picked at a still later stage. 
Controls = Twenty mature seeds gathered during previous season. 
Seeds sown in garden soil. Temperature i5°-2o c 
Number of Germinations after : 
c. 
Lot I 
5 days. 
o 
io days. 
i (19 dead) 
14 days. 
„ II 
20 
20 (18 healthy) 
— 
„ I 
o 
0 (all dead) 
— 
v II 
20 
20 (all healthy) 
— 
„ I 
— 
10 (10 ungerminated dead) 
/_ — - 
„ II 
— 
26 (all healthy) 
— 
ontrols] 
20 
— 
18 
If the testa is not removed a large proportion of the seeds perish 
when sown. The most immature seeds tested showed a high mortality, 
but as maturity was approached so the injurious effect of the testa was 
decreased, nevertheless the seeds that survived showed an appreciable delay 
in germination. No real dormancy similar to that described above in the 
case of Brassica alba was observed . 1 
In order to test our hypothesis that the effect of the testa, as shown in 
the experiments above, is to be attributed to its property in limiting the 
gaseous exchange of the embryo, further experiments were carried out in 
1 It is interesting to note here that this is the same relation between seeds of Brassica alba and 
those of Pisum sativum in regard to dormancy as that found when the germination of these seeds 
was inhibited by atmospheres containing certain percentages of carbon dioxide (cf. Kidd, 9). Seeds 
of White Mustard exhibit secondary dormancy when removed to air. No such phenomenon can be 
obtained with peas. 
