them in the proportions of heartwood and sapwood, and usually has 

 a greater proportion of the former than yellow pine. 



SILVICAL FORMS. 



With a range extending over more than 2,000 miles from north to 

 south and almost 1,000 from east to west, Douglas fir grows under 

 more diverse climatic conditions than any other important American 

 timber tree. In various parts of this range it produces forms of 

 growth sufficiently diverse, in the opinion of some foresters, to be 

 called varieties, or even species. Whatever its botanical status, it is 

 certain that in its silvical characteristics and requirements Douglas 

 fir presents two well-marked forms. 



These may be contrasted as the form of Jjest development and the 

 form of hest resista?ice. The first is well defined on the Pacific coast, 

 where conditions are favorable for rapid growth to its largest size; 

 the other in the Rocky Mountain region, where less favorable cli- 

 matic influences limit its rate of growth and size. In the moderately 

 humid climate of northern Idaho and northwestern Montana the 

 two forms seem to intergrade and the tree reaches a large size in 

 moist situations at low altitudes, but is smaller in drier places and 

 at higher elevations. Different methods of silvicultural treatment 

 are required for the two forms, partly hj the widely varying nature 

 of the forests in which they grow and partly by the different natures 

 of the trees themselves. 



VARIATIONS BETWEEN THE COAST AND MOUNTAIN FORMS. 



The differences between the Rocky Mountain and coast forms of 

 Douglas fir are both physiological and morphological. They include 

 variations not only in rate of growth and sensitiveness to frost, but 

 also in the form of the tree, the size and shape of the cones, the char- 

 acter of the foliage, and even the grain of the wood. Many of these 

 differences are in themselves insignificant, but when both forms are 

 raised side by side from the seed the cumulative effect is very striking. 

 ♦ The most apparent of these variations is in the rate of groAvth. In 

 the German forest experiment station at Graf rath, IT-year-old trees 

 of the coast and Rocky Mountain forms which were grown together 

 in the same soil reached average heights of 26 and 7.5 feet, respec- 

 tively. At Groenendael 13-year-old trees of the coast form averaged 

 21 feet in height and 3^^ inches in diameter, while 12-year-old moun- 

 tain firs growling beside them were only 9f feet high and less than If 

 inches in diameter. In a 7-year-old Scotch plantation a t^^pical 

 specimen of the mountain form was 8 feet 10 inches high, while a 

 tree of the coast form, standing 4 feet away, had attained a height 

 of 15 feet 6 inches (fig. 1). 



[Cir. 150] 



