SITKA SPRUCE, WESTERN LARCH, AND DOUGLAS FIR. 201 



Colorado, and scattered more or less throughout Arizona, New 

 Mexico, north-west Texas, and northern Mexico. 



It may be noted that Douglas fir is not found in the regions 

 where Sitka spruce reaches its optimum. Douglas fir is absent 

 from the western side of Vancouver Island and the coastal 

 archipelago, that is, from the regions of large precipitation and 

 heavy fogs where the spruce is found at its best. The mountain 

 form of Douglas fir is found associated to a greater or less 

 extent with western larch throughout the range of the latter 

 species. 



Much interest has been shown in regard to the variations or 

 forms of Douglas fir. In the first place, it must be evident to 

 foresters that with conifers especially, the leaves, buds, and 

 bark vary on different parts of the crown and stem, and that 

 cones differ in size on the individual tree, and more especially 

 when young and old trees are compared. However, the largest 

 seeds and greatest yields are got from medium-aged large trees, 

 growing in open stands in warm locations and low altitudes. 



The size of the seed depends largely on the size of the cone, 

 and this again is directly dependent upon the vigour of the 

 cone-bearing shoot, hence young trees produce the largest, but 

 not the most abundant seed, and old trees the smallest seed. 

 This is reflected in the larger size of the one and two year-old 

 seedling plants from seed collected from young open-grown 

 trees. 



Some botanists maintain that the Douglas fir of the Pacific 

 Slope and of the Rocky Mountains are distinct species. United 

 States dendrologists, however, do not agree with this view. 

 After long experience and research, they maintain that there is 

 nothing to warrant specific distinction between these two 

 regional forms. The characteristics which seemingly separate 

 them are not reliable, the real difference being of a silvicultural 

 nature. 



Moreover, specific distinctions really lie in the. reproductive 

 organs, and not on the size and form of the tree, the size of 

 cones and leaves, or in the thickness of bark. Douglas fir, 

 therefore, when we remember its wide distribution and the 

 varying climatic conditions under which it grows, may for all 

 practical purposes be safely regarded as a polymorphic species. 



VOL. XXXVI. PART II. 



