173 JOURNAL OF FORESTRY 



The studies indicate, however, that for western hemlock no regular 

 periodicity of cone crops could be determined. If there is some in- 

 herent rhythm in the production of heavy crops of seed of this tree it 

 was not discovered. It is very doubtful that there is such. 



Age of Seed-bearing. — It was definitely shown by the study that the 

 age at which hemlocks first begin to bear seed is entirely subject to the 

 conditions governing the growth of the tree. It was found that al- 

 though one hemlock may bear a heavy crop when twenty years old or 

 less, another tree alongside of it may bear none, or but very few, until 

 much later in life. This is due to stimuli which affected the heavily 

 bearing tree alone. It is believed that some hemlocks bear no heavy 

 crops until at least a hundred years old, even though growing under 

 healthy conditions. In this regard it is interesting to note that small 

 saplings were found which although but ten or fifteen years old bore 

 seed copiously. 



Quantity of Seed Produced. — The important point in this connection 

 perhaps is the fact that trees of all sizes, from small saplings to large, 

 full-crowned trees, at times were found simply covered with cones. 

 One 25-year-old tree, which had been growing about a foot a year in 

 height until fatally injured by bark borers, by actual count bore 1,445 

 cones in one year. Cone counts were made of several large trees which 

 had grown vigorously in the open by counting the cones on a number 

 of branches and then applying the result to all the limbs of the tree. 

 The trees obviously were fruiting heavily, but the actual results were 

 astounding. It was found that such trees at times bore 15,000 cones in 

 a single year. Many trees observed had borne from 5,000 to 10,000 

 cones a year for several years. The cones of western hemlock are 

 small, seldom being over an inch long, but each cone contains about 

 forty seeds. These trees, therefore, produced over 500,000 seeds in 

 one year. 



Naturally the larger the tree the more sprays it has and the more 

 cones it can bear. In this respect it is self-evident that a mature tree 

 can bear more cones than an immature tree. The trees which bore the 

 heaviest had been injured after having enjoyed a long period of rapid 

 growth. The amount of seed produced by thrifty, uninjured hemlocks 

 in general is most decidedly less than those which were bearing as a 

 result of stimulation through injury. 



In this connection Zon's conclusions from his study of the seed pro- 

 duction of western white pine (loc. cit.) are of interest: Conclusion 

 five states : "The vigor of growth apparently influences favorably the 

 amount and quality of seed produced. Thus trees which grew at the 



