248 
THE NATIONAL NURSERYMAN 
Rate of Germination— 
Naturally the rate and total germination of each species is of 
considerable interest. These are given in Table I. These do 
not include all of the earlier tests, many of which were made 
under too low temperatures, but they show what may be ex¬ 
pected from fresh unimpaired seed under favorable greenhouse 
conditions, and give more usable average figures than if all of 
the tests were averaged indiscriminately. 
Germination ancl Temperature of the Medium — 
Of all factors which affect results in seed testing, that of tem¬ 
perature is perhaps the most important, for no germination will 
take place except under favorable degrees of heat. Some of 
these relations are set forth in Table II. 
TABLE II 
Average Germination Per Cent. Per Day Under Different Tempera¬ 
tures During the Most Active Period 
Species 
50-60 
Degrees 
60-70 
F. 
70-80 
% 
% 
% 
Pinus ponderosa . 
. 0.2 
1.0 
1.4 
Pinus monticola . 
. 0.0 
0.0 
1.25 
Pinus monticola (Ti-ps cut) . 
. 0.25 
0.25 
1.8 
Pinus contorta . 
. * 
5.0 
Pseudotsuga tax. 
. 0.4 
1.5 
2.5 
Picea engelmanni . 
5.8 
11.0 
Thuja plicata . 
0.1 
4.0 
Tsuga heterophylla . 
. . 
4.3 
* Data lacking. 
During the five years of testing seed at the Experiment Sta¬ 
tion, it was found that all of the species with which we are 
concerned germinate satisfactorily when the sand temperature 
has a daily mean between 70o and 80o F. and when the daily 
maximum sand temperature went up to 90 and 95o F. Temper¬ 
atures of 100o F., though not injurious to all species, should be 
avoided. 
Hastening Germination of Rebellious Seeds — 
The question often comes up to what extent the germination 
of coniferous seeds may be hastened by artificial means. In 
the case of western white pine seed, which does not give com¬ 
plete germination in the nursery during the first summer, some 
means of stimulation is a necessity, both for economy and the 
production of uniform stock. 
Some of the means of hastening germination of this species 
are as follows: 
1. Reduction of the seed coat by chemical corrosion, prefer¬ 
ably by immersion in concentrated sulphuric acid for forty min¬ 
utes, followed by very thorough rinsing of the seed. Sowing 
before drying. 
It should be made clear at first, however, that the habitually 
delayed germination of western white pine has been found to 
be due to the hard cellulose seed coat which resists entrance of 
water for some time, and not, as some have supposed, to after¬ 
ripening of the seed following the maturing of the cones. The 
processes of stimulation must therefore be directed toward re¬ 
ducing or dissolving this seed coat by mechanical or chemical 
means or by a softening process. The mechanical processes of 
abrasion or pearling cannot well be employed because a very 
small degree of pressure or friction kills the seed. 
2. Soaking the seed in water for twenty-four hours and ex¬ 
posing it to freezing temperatures. Alternate thawing and 
freezing is not considered harmful provided the seed does not 
mold or if temperatures remain so low that germination does 
not begin. 
3. Abrasion of the seed coat is a means of hastening germin¬ 
ation, but in this' way it is impossible not to injure the seed to 
a considerable degree. 
4. One of the safest and most effective ways is to mix the 
seed with clean bark-free sawdust and to keep it in a warm 
place for three weeks. The sawdust and the seed must be 
stirred once each day to counteract development of molds. 
Deterioration of Stored Seed by Age — 
It is known that stored seed of all species will lose vitality 
from year to year even with the best of care and precaution 
against dampness, drying out or extreme temperatures. Very 
little is known, however, regarding the exact rate of this de¬ 
terioration. 7 This knowledge is of special interest to those 
who must collect and store large quantities of seed at con¬ 
siderable cost. 
7 Since writing this article an important contribution to this 
knowledge has appeared in the work of C. R. Tillotson, Jour. Agri¬ 
cultural Research, Vol. XXII, p. 479, 1922. 
