FOREST msTKIHrTION 



pe in the Bitter Koot and the .locko Valleys. Even low undu- 

 lations on the mountainside j)reseut the same aspect. Where 

 the direction of the slopes fails to present a sufficient contrast 

 of conditions the transition is more gradual and scattered forest 

 tivcs a IT sprinkled through the grass land diminishing in si/e 

 and numbers with the increase in distance from the main stand 

 until the farthest limits of the forest are represented by a few 

 low pines set at wide intervals. A tension between the prairie 

 and the forest is evident. It is also evident that the forest is 

 gradually replacing the grasses. Here the pine leads the way 

 followed closely by the Douglas spruce, these two and rarely 

 other species. .///// in< nis scopulonun. The miurat ion is usually 

 from above downward, but local conditions may vary this and 

 shew a miuration from wooded canyons onto the neighboring 

 prairie, ^n interesting reversal of the usual course is to be 

 M on Wild Horse Island in Flathead Lake, where the forest, 

 iroverned apparently by the proximity of the lake waters, became 

 established first at the foot of the slopes and is gradually oc- 

 cupying the higher ground. 



Owing to local features of the physiography the directions 

 of the wooded and barren silopes may be altered, or even re- 

 versed. The western slopes of the Mission Range, rising from 

 Flathead Lake are densely wooded and steep, while the opposite 

 shore, a scries of low foothills, is mainly urass-land. The evi- 

 dent explanation here lies in the influence of the lake upon the 

 moisture content of the westerly winds. The foothills of the 

 west shore lie in. the rain-shadow of the Cabinets, a high raiiLM> 

 t" the west. Narrow valleys or canyons extending north and 

 south and transverse to the direction of the west winds some- 

 times show the western slope more heavily wooded than the 

 ^'ern. This fact is due. apparently, to the protection from the 

 desiccating influence of th,. westerly winds afforded by Hie 

 mountain opposite and the normally higher temperature of a 

 w^t, TII exposure. In the vicinity of Ilangan. near the western 

 boundary <'f the State. t!i;- dry exposures are distinctly north- 

 ern. This locality was on-e heavily forested but many years 

 was denndcrl by fire. .\ series of s|.,pe S IK-IT shows a sharp 

 'i the Miutliwot.-ni and western exposures which 

 were, at the time of the observation, in HMO. producing a sturdy 



