246 Part III. Chapter 3. 
The northern Rocky Mountains north of the Big Horn River valley includi 
the mountains of Idaho and Montana, northwestern Wyoming and eas 
British Columbia, Alberta and northward were tenanted from several m 
directions, viz., the north east and the east; the west and southwest. Farin 
the northern part of the interior of British Columbia and Alberta is found just 
such an assemblage of plants, as occur in’ many parts of eastern Cana 
though mingled with unfamiliar plants. This flora appears to run compl 
across the continent north of the great plains and it characterizes a region 
moderately heavy rainfall, summers not excessively warm and cold winte 
Thirteen species of trees and shrubs entered the northern Rocky Mountai 
from the northwest Pacific coast: 
Abies grandis Lindl. Prunus demissa Walp. 
Larix occidentalis Nutt. Menziesia ferruginea Smith. 
Sorbus sambucifolia Cham. & Schlecht. Lonicera utahensis Watson. 
Rosa gymnocarpa Nutt. ' Phyllodoce glandulifera Hook. 
Chrysothaminus viscidiflorus Nutt. Ledum glandulosum Nutt. 
Prunus emarginata Walp. 
Spiraea pyramidata Greene. 
Echinopanax (Fatsia) horridum Smith. 
Five species of a similar origin pursued a somewhat similar direction, but 
migrated eastward to the Black Hills and Lake Superior, viz., 
Salix fluviatilis Nutt. (= P. longifolia Muhl.). | 
California to British Columbia, east to Missouri and Kentucky. 
Artemisia frigida Willd. ? 
Idaho, Montana, Minnesota, Saskatchewan. 
Menziesia glabella Gray. 
regon, British Columbia, Bitterroot mountains ‚ Flathead 
Mont. to Lake Superior. 
Spiraea lucida Dougl. (= S. betulifolia Pall.). 
British Columbia, Oregon, Montana, Black Hills. 2 
Vaccinium membranaceum Dougl. (= V. myrtilloides Hook.). 
Flathead Lake, Bitterroot mountains, Alaska, California, east £ 
Lake Superior. n 
n. 
‚The following twenty six species of Pacific coast shrubs and trees raM 
from California northward, but in Washington and Oregon, they turned ® 
ward and entered the northern Rocky Mountains of the United States & 
British America, extending only, as far, as the Bitterroot Mountains in Ida i 
perhaps in later glacial times when the floral intercommunication of the north 
Cascades with the northern Rockies must have been very free. 
Pinus albicaulis Engelm. Artemisia ludoviciana Nutt., Bitterroot8- 
»  monticola Dousol. Berberis nervosa Pursh, BitterrootS- 
Alnus rhombifolia Nutt. (Nutt. | Cornus Nuttalli Audub., Bitterroofs- 
Artemisia discolor Dougl. var. incompta »  pubescens Nutt., Bitterroots- 
