Contribution from the Forest Service, Henry S. Graves, Forester. 
April 17, 1915. 
(PROFESSIONAL PAPER.) 
44 Ps 
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SEED PRODUCTION OF WESTERN WHITE PINE.' 
By RapHaet Zon, Chief of Forest Investigations. 
PROBLEMS INVOLVED IN DETERMINING SEED PRODUCTION. 
_ When, several years ago, an attempt was made by the Forest Serv- 
ice to collect seed on a large scale for forestation purposes, it was 
- keenly realized for the first time how little knowledge exists in this 
country regarding the seed production of our trees and the factors 
which influence it. One should be able to foretell with a reasonable 
degree of certainty the amount of seed which different species will 
produce at definite intervals. Aside from the practical value of 
such knowledge, it is of the greatest scientific interest. Our knowl- 
edge of the life history of forest trees will be incomplete until the 
_ mysterious occurrence of seed years and the factors that influence 
_ them are fully understood. Of all the forest problems, seed pro- 
5 duction is the most difficult one to solve. This may be readily 
inferred from the fact that although seed production excited great 
interest on the part of European fore ters even in the early days, and 
several attempts were made to penetrate into the mystery of it, 
F little as yet is known regarding the factors which influence the od 
production of even the few Kuropean species. 
E The investigation of seed production of forest trees consists of four 
‘distinct problems: (1) The determination of the amount of the seed 
_ crop, (2) the determination of the periodicity of seed production, (3) 
_ the determination of the various external and internal factors which 
affect the amount and the periodicity of seed production, and (4) the 
solution of the biological problem of seed production. Each of these 
problems must be solved in the order indicated, since the solution of 
_ one furnishes the basis for the solution of those which follow. 
% The first and immediate problem is to determine the amount of 
= produced by each species. This may not'be as simple an under- 
1 Pinus monticola Dougl. 
Note.—This bulletin contains a report upon an investigation of the seed production of western white 
‘pine and a discussion of the method of measuring the seed crop. 
85754°—Bull. 210—15 
