488 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



6. Southwestern foothills of Northern Rockies 

 In central Idaho the foothill flora is very meager as far as 

 woody plants are concerned. Bull Pine is practically wanting, 

 and both the oaks and junipers have disappeared. The woody 

 vegetation of the drier hillsides is mostly made up of shrubs, 

 such as species of Artemisia, Chrysothamnus , Tetradymia, Eurotia, 

 etc. The mountain mahoganies, Cercocarpus ledifolius and C. 

 hypoleucus, are also found there. Along the water courses are 

 found species of Popuhis, Salix, Crataegus, Amelanchier, Betula, 

 and Alnus. 



7. Western foothills of the Northern Rockies 

 In British Columbia there are no foothill regions of the Rockies, 

 for, as said before, they connect here through several mountain 

 ridges with the Cascades. I have not visited personally the west 

 side of the Bitter Root Mountains, but have received the impres- 

 sion from what I have read that there is a broad belt of Yellow 

 Pine, Finns ponderosa, on the higher plains bordering these 

 mountains. These woods Piper includes in the arid portion of 

 the Transition Zone. Judging from the little I have seen of the 

 Flathead Basin between the Rockies proper and the Bitter Roots, 

 one may scarcely speak of any distinct foothills, as no other transi- 

 tion flora exists there than what we find in any mountain valley 

 between the hillsides and the bottomlands. 



As seen from above, the Pine Belt only, consisting of scattered 

 Finns scopulorum and Sabina scopulorum, is present on the eastern 

 slope of the Northern Rockies and the northeastern slope of the 

 Southern. In the southern part of the western slope of the 

 Northern Rockies where the Bull Pine is absent the belt is also 

 absent as a Pine Belt and in the northern part its place is taken by 

 F. ponderosa. As Finns scopulorum is the one of the mountain trees 

 that grows at lowest altitudes, it naturally is the tree that runs 

 further down on the hills or further out on the plains, and is the 

 one that really is concerned in the strife between the mountain 

 forest and the grasslands of the plain, or lietwcen the IMontane 

 evergreens and the Submontane deciduous trees. It is one of the 

 important components of the Montane flora and should be counted 

 there, but as it encroaches so much on the Submontane floral 

 districts, and its close relali\-e, Finns ponderosa, is the charac- 



