THE WESTERN VALLEYS 119 



up briefly as follows: The trees begin early to bear seeds and 

 produce them in abundance throughout a long life. The seeds 

 are small and light, and provided with ample wings by which 

 they are carried far by the wind. In addition to these quali- 

 ties they retain their viability well and usually show a good 

 germination percentage. When once started the seedlings grow 

 rapidly in height, a feature in which they excel most other 

 species. With age the tree acquires a thick bark which serves 

 it well as a protection from ground fires. 



The negative or limiting qualities are seen in the intolerance 

 of the larch to shade, in its rigid demands upon soil moisture, its 

 partiality to cooler climates and its marked susceptibility to 

 disease. 



The strong points of the larch are in its seeding habits, and 

 its rapid early growth. The significance of the positive factors 

 is especially evident in local distribution. The seeding ability 

 of the tree often enables it to occupy limited areas exclusively, 

 but such areas are bounded by the special properties of the soil 

 from the moisture standpoint. The temperature relations of 

 the species are such that its most southerly extension in the 

 Rocky Mountains occurs in Montana, and it doubtless is found 

 farther south than it otherwise might be were it not for the 

 topographical conditions which provide suitable situations on 

 northern slopes. While the western larch endures a considerable 

 diurnal range of temperature, it is distinctly a tree of the cooler 

 regions. It is one of the principal trees of the Kootenai Valley, 

 where the annual range of temperature may be from -40 to 108 ; 

 the days of summer may be hot, but the nights usually are cool 

 and frosts occur in all months of the year. 



The rapidity of its early growth in height is probably the 

 most important of all its qualities in competition with other 

 species. Under good conditions trees make a growth of 4 feet 

 in 4 years while under the same conditions Douglas spruce gains 

 a height of about 20 inches, yellow pine about the same and 

 Engelmahn spruce less than a foot. Thus if given an equal 

 chance, or even somewhat less, the larch will soon be so far above 

 its neighbors as to be out of all danger from shading. Engel- 

 mann spruce sometimes forms forests so dense that nothing can 

 grow beneath their crowns, yet in just such forests one may 



