RELATION OF STIMULI TO CONE PRODUCTION 169 



the Forest Service to collect seed ... 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." "Our 

 knowledge of the life history of forest trees will be incomplete until 

 the mysterious occurrence of seed years and the factors which influ- 

 ence them are fully understood." "Little as yet is known regarding the 

 factors which influence the seed production of even the few European 

 species," . . . although these species have been studied for a great 

 many years. ^ 



In 1914, during a rather extensive investigation of the reproduction 

 of western hemlock while at the University of Washington, the rela- 

 tionship between heavy seed crops on individual trees and distinct 

 external causes was quite accidentally hit upon. Once found, however, 

 and with the relationship confirmed by the contributory evidence which 

 the botanist offered, the line was eagerly followed during the school 

 term. 



Very little is found in our American literature concerning the rela- 

 tion of stimuli to the seed production of trees. G. A. Pearson, of the 

 U. S. Forest Service, has conducted some preliminary investigations 

 along this line. His published conclusions, however, deal "primarily 

 with the conditions (of the tree) affecting the germinative quality of 

 the seed" ; the "influence upon the quantity of seed, though of great 

 importance," is "treated only as a secondary topic," because the data 

 were incomplete.^ Such of his conclusions as are considered pertinent 

 and of value are included further on in this article. 



The investigation as conducted on western hemlock was simply one 

 of observation. Due to lack of time, no verifying experiments were 

 completed, but the data as gathered appear to warrant some preliminary 

 statements. 



In most forest investigations correct deductions are more easily ob- 

 tained from affirmative data than from negative data. Of a hundred 

 trees in the forest, possibly but two or three bear heavy crops. To 

 determine why the ninety-eight trees are not bearing heavily is of less 

 importance in the solving of this problem, and, of course, much more 

 costly and difficult, than to determine why the two or three are bearing 

 heavily. With this consideration in mind, the method of attack of the 

 problem was to locate western hemlock trees which were bearing ex- 

 ceptionally heavy crops of cones. 



"'Seed Production of Western White Pine." Raphael Zon, Chief of Forest 

 Investigations. Bull. 210, U. S. Dept. of Agriculture, 1915. 



' "The Ape and Condition of the Tree upon the Seed Production of Wi'stcrn 

 Yellow Pine." U. S. Forest Service, Circular 196, 1912. 



