KOKKST DISTRimTION 



leaved, deciduous vegetation, is dominant, as a rule, only along 

 th<- bottom hinds and stream hanks. It is hardly too much to say 

 that in these places nine-tenths of the forest consists of the spe- 

 r<>l>uhis, Stili.r, A/tins and I!<hil(t. On the western slope 

 J'aimhtx frtc/nK-<iriKi is the only large cottonwood of the river 

 hottoms. It is usually aeeompanied by Ainu* /< nnifolid and 

 ]>ttnld. foiiiiiidHs. These three species are found along every 

 stream on the western slope. Along with these, usual or fre- 

 (jiicnt. are J'OJXI/HS tr< tmtloidcs, Salix cordata, 8. flnrintilis, 

 Cornus stol&nifera, etc. 



On the eastern slope and the plains the bottomlands are 

 commonly covered with Populus Sargcntii, accompanied more or 

 less frequently by P. tremuloides, Salix flu rial His, Jlctitla. fon- 

 H mi! is, Amelanchier alnifo'ia, Acer Negundo, Lcpargyraca ar- 

 ;/< n tea, etc. 



As to the upper limit of tree growth there seems to be no 

 clearly defined timber line except such as may be due to the 

 desiccating influence of wind. Only the crests are usually bare 

 or occupied by stunted pines, spruces or firs and this way <><- 

 <-nr at relatively low altitudes of 6000-7000 feet, while on neigh- 

 boring mountains of greater elevation forests may be found ex- 

 tending much higher up the slopes. Other factors, like the steep- 

 nd rni^edness of the land have much to do with the matter 

 of forest occupation both as to moisture and as to foothold. 

 Consequently hi.u-h and pinnacled crests like the southern peaks 

 of the Mission If an ye. the Bitter Roots from St. Mary's Peak- 

 to the Xex IVrce Pass, the precipitous declivities of the main 

 range r the Rockies from (Jlacier Park to Lewis and Clark 

 the liiirh summits south of (ieoru-etnwn, all are barren, due 

 in part to their dcvated exposure and to the inhospitable eharae- 

 ter of their surface. Klsewhere the high elevations of rounded 

 contour are 1'on-strd .smiM-t inies by pines, firs or spruces, some- 

 times by an open stand of Rocky Mountain juniper ( ,/ . sco/ni- 



"> as shown near the Miillan Pass and the Continental Di- 

 vide southeast of Bntte. 



Tin- principal tn-i-s in the forests west of the Divide are 

 Pinus ponderosa, /'. T/////O/-/,/ and /'. dlhicaiilis, Larir <>ccidcntalis f 

 P$eudotsuga taxi folia, l'i<<n Kmjtlnnnuiii, Altics Insioca-rim. and 

 .//'//// Oplllorum. Lorally /'inns nionl icola, Tsinjn hctero- 



