THE WESTERN VALLEYS 129 



being low in vitality and germination are a means of slow and 

 uncertain reproduction. 



The grand fir is impartial to soils as to structure and compo- 

 sition, provided they are sufficiently moist. It is usually found 

 on bottom lands or in places where the soil is likely never to be 

 dry. Even under the favorable conditions which usually pre- 

 vail over most of the country west of the Cascades, this fir is 

 usually found on river banks or in the bottoms of canyons, where 

 it reaches large dimensions. In western ^Montana the relation 

 to soil moisture is even more strongly emphasized. 



The grand fir seems to demand on the whole a higher tem- 

 perature than the white pine. Its lower limit is about -30 de- 

 grees while its upper range is some degrees above the maximum 

 commonly understood for Avhite pine, or somewhat over 100 de- 

 grees. In Oregon this species thrives at sea level while the white 

 pine seldom appears there below 3000 feet. 



Fire injury in this species is seldom an important matter 

 as the local conditions on river bottoms and similar places are 

 not often such as to invite it. The matter of disease, except 

 for Echinodontvum tinctorium, is not apparently a serious one. 



The control of distribution in this species, therefore, must 

 be largely topographic, with reference to the amount of soil mois- 

 ture, and on areas which are favorable its size and numbers are 

 determined by competition. 



The hemlock (Tsuga heterophijlla) affords another example 

 of a conifer of mesophytie requirements. In fact it is mvich more 

 restricted in its local distribution than the grand fir. Its range 

 in western Montana is confined to localities in the northwestern 

 part of the State, in the valleys of the Swan River, the Flathead 

 and the Kootenai. It is found in the valley of McDonald Creek 

 in Glacier Park, and a stand of trees uniisually large for this 

 region occurs in Avalanche Basin, tributary to the same stream. 



In its positive qualities the hemlock is particularly fortunate. 

 These pertain to two features, its seeding habits and light rela- 

 tions. Abundant, seeds are produced, which have a high germ- 

 inative capacity and the ability to thrive on the humus cover 

 and litter of the forest floor. The seeds, being light and with 

 ample wings, may be carried well by an ordinary breeze. The 

 hemlock is very tolerant of shade and is of fairly rapid growth. 



