o-vno^s 
METHODS OF STIMULATING GERMINATION OF WESTERN 
WHITE-PINE SEED 1 
By J. A. Larsen 
Forest Examiner, Priest River Forest Experiment Station, Forest Service, United 
States Department of Agriculture 
INTRODUCTION 
In forestry as in agriculture seeds are often encountered which are 
difficult to germinate and are called “rebellious.” In this class 
belong the seeds of many hardwood species and not a few conifers. 
The soft or white pines are much noted for this characteristic, Pinus 
monticola in particular. 
Prompt germination of western white-pine seed has constituted 
a real problem in the Forest Service nurseries of the northern Rocky 
Mountain region. In one instance 35 beds spring-sown with 5 pounds 
of seed per bed gave a meager and irregular germination the first 
summer and from 3,000 to 40,000 seedlings per bed the second season. 
Such results add greatly to the expense of raising nursery stock, in 
that the beds require care for two years instead of one and occupy 
double the usual space. 
When this problem was taken up by the field station of the Priest 
River Forest Experiment Station, in northern Idaho, it was assumed 
as a working basis that delayed germination was due to inherent 
physiological characteristics requiring after-ripening of the seed or a 
period of rest, 2 or to the impermeability of the seed coat to water from 
without and to the root tip from within. If the first hypothesis were 
true, some process of stimulation by stratification or by chemical or 
physical means might be effective. If the latter were the case, 
reduction of the seed coat by chemical or mechanical means would be 
likely to bring success. 
German investigators, among them E. Zederbauer, 3 who has done 
considerable work with conifer seeds, maintain that there is a relation 
between the time of ripening and of germination, and that the seed 
which is shed in the autumn germinates slowly while that which is 
shed in the spring germinates more rapidly, Zederbauer places 
Abies alba , Pinus cerrnra , and Pinus strobus in the slow class. The 
seed of these fall in the autumn. Pinus sylvestris, Pinus nigra , 
Picea excelsa , and Larix europea he places in the rapidly germinating 
class. The seed of this latter class is shed in March, or, as with 
Picea excelsa , in February. The seed which remains on the ground 
during the winter is subjected to the influences of water and frost, 
differences in ground conditions and other factors, all of which may * 
produce chemico-physiological changes. 
Early work on this project at the Priest River Forest Experiment 
Station embraced treatment with sulphuric acid and other chemicals. 
1 Received for publication Dec. 22, 1924; issued January, 1925. 
2 Coulter, J. M., Barnes, C. R., and Cowlbs, H. C. a textbook of botany for colleges and 
UNIVERSITIES, v. 2, p. 931-932, illus. [1911.] 
2 Zederbauer, E. die keimprAfungsdauer einiger koniferen. Centbl. Gesam. Forstw. 32: 
306-315, 1906. 
Journal of Agricultural Research, 
Washington, D. C. 
( 889 ) 
Vol. XXXI, No. 9 
Nov. 1, 1925 
Key No. F-29 
