4 82 Kidd and West . — The Conti' oiling 
placed in an atmosphere of pure oxygen at 75 mm. Hg pressure, i. e. a tension 
of oxygen equal to half that in air. This treatment had no effect in 
stimulating the germination of seeds showing secondary dormancy and 
indicates that an inhibiting concentration of carbon dioxide in the tissues 
is not the cause of secondary dormancy. 
Acids. 
Crocker and Davis ( 5 ), working with dormant seeds of Alisrna 
Plantago , concluded that the effect of acids in producing germination was 
due to their weakening action upon the seed-coat. Eckerson (11), however, 
showed that in the case of Crataegus mollis , Pyrus mains , &c., dilute acids 
also affected the internal factors controlling the length of the so-called 
after-ripening period, while Lehmann ( 12 ) found that the action of acids 
and of certain hydrolysing enzymes can replace the action of light in 
producing the germination of dormant light-sensitive seeds, and took the 
view that hydrolysis is the important factor, but in this connexion it should 
be pointed out that he does not clearly distinguish between the seed-coat 
and the embryo itself. 
Experiments were conducted to test the effect of dilute acids upon 
White Mustard seeds showing secondary dormancy. Hydrochloric and 
propionic acids were used. It was found in result (Table XXIII) that the 
effect of acids in increasing concentration was as follows: With HC 1 , for 
example, the lowest concentration used, namely 
N 
N 
I. GOO 
had little effect, 
whilst higher concentrations (— ) induced germination, but subsequently 
& v ioo / N 
killed the primary root. Similarly, — propionic acid caused 80 per 
cent, germination in two days, but subsequently killed all the seeds. 
Table XXIII. 
Treatment of the 
inhibited seeds. 
Water 
Number of 
seeds used. 
25 
Percentage of germinations after — 
12 3 4 5 6 7 9 10 
day. days . days. days. days. days. days. days. days. 
0 0 12 16 20 20 20 20 20 
N HC 1 . 
1 ,000 
dd HC 1 . 
100 
20 
0 
0 
0000 
0 5 10 
All dead. 
20 
20 
30 
40 45 60 65 
65 65 65 
dd Propionic acid. io 
100 
0 
80 
All dead. 
A’ 
— Propionic acid. 
10 
0 
40 
All dead. 
Mean temperature of laboratory, i6° C. 
The results of these experiments with acids lead us to a conclusion 
similar in nature to that already stated with regard to the action of 
temperature, namely, that germination of dormant White Mustard seeds 
