BULLETIN OF TH 



MPfflflOFA 



No. 210 



Contribution from the Forest Service, Henry S. Graves, Forester. 

 April 17, 1915. 



(PROFESSIONAL PAPER.) 



SEED PRODUCTION OF WESTERN WHITE PINE. 1 



By RAPHAEL 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- 

 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 foresters even in the early days, and 

 several attempts were made to penetrate into the mystery of it, 

 little as yet is known regarding the factors which influence the seed 

 production of even the few European species. 



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 

 seed 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. 21015 



