892 
Journal of Agricultural Research 
Vol. XXXI, No. 
Samples of seed were frozen in an ice-cream freezer for 6, 12, 1&, 
and 24 hours after having been soaked in cold water to test the 
effect of the mechanical action of freezing. One sample was soaked 
in full-strength sulphuric acid 15 minutes, thoroughly washed, 
and frozen for 24 hours; another was frozen 24 hours and then 
heated in the incubator for 3 days. 
The results of these treatments and of the several check tests, 
as well as of samples with holes cut in the seed coat, are given in 
Table II: 
Table II .—Highest germinations obtained by soaking , freezing , and chemical 
treatments 
No. 
Treatment 
Time 
Ger 
Uncov¬ 
ered 
minatioE 
.(250 ( 
Moss 
mulch 
in seed bed 
lays) 
Check tests 
Uncov¬ 
ered 
Moss 
mulch 
: 
Per cent 
Per cent 
Per cent 
Per cent 
1 
Sulphuric acid_ 
45 minutes_ 
38/5 
28.5 
4.5 
3,5 
,2 
Sulphuric acid, then heated 144° by water and 
_do_ 
40.5 
30. Q 
6.0 
5.5 
left standing 30 minutes. 
3 
Acetic acidu. *..... 
40 minutes_ 
7.0 
14.0 
5.5 
10.0 
4 
Citric acid---..--- 
120 minutes... 
7.0 
5.5 
8.5 
2.5 
(Sulphuric acid.--- ... -- 
15 minutes_ 
1 
- 
< Freezer^-j-i _______ 
24 hours.. 
}. 11.0 
26.5 
7.0 
10.0 
[(Incubator..._ _... ___ 
3 days_ 
| , 
^ 6 
^Pottfesiflbi fSerinanganate-- 
180 minutes... 
19.5 
19.5 
7.5 
7.5 
' 7 
Potassium sulphate_:.. 
120 minutes... 
26.5 
24.5 
5.5 
4,0 
8 
Carbolic acid—_ 
30 minutes_ 
15.0 
12.5 
5.0 
4.0 
9 
Tipp worn bv rubbing on file_ 
34.0 
21.0 
io 
Tip® cut with knife_^_ _ 
51.0 
56.0 
ii 
Seed coat cracked by crushing. __ 
0.0 
1.0 
12 
Seed coat split open with knife__ 
41.0 
29.0 
13 
Hole cut in seed coat, leaf end __ _ 
40.0 
22.0 
44 
Soaked in sulphuric acid until seed coat could be 
24.0 
42.0 
rubbed off. 
~15 
Seed coat entirely removed __ 
43.0 
4.0 
» 
” 
■ 
, In the tests with chemicals the highest nursery germination of 38.5 
per cent was obtained by soaking the seed in concentrated sulphuric 
acid for 45 minutes. The addition of water to produce heat raised 
this to only 40.5_per cent and is not considered a sufficient gain to be 
worth while. The treatments with the other chemicals resulted, on 
the whole, in very little stimulation. The soaking in acid 15 minutes 
with later freezing and heat treatment produced germination no 
better than soaking in sulphuric acid 35 minutes without freezing. 
Freezing as well as heating by these methods would therefore seem 
to he Useless operations. 
Not only a greater total germination but a more rapid rate than in 
the sulphuric acid tests was obtained by the mechanical treatments, 
especially the cutting of a very small hole in the end of the seed with 
ft Knife. (See fig. 1.) Mechanical abrasion of the seed coat, if it 
can be done without injury to the kernel, is therefore sure to give a 
higher and more rapid germination than either stratification or 
chemical corrosion of the seed coat. 
* Preliminary treatment to stimulate the germination of white pine 
by soaking in sulphuric acid is a practical and efficient method which 
