SOURCES OP THE VEGETATION 73 



Salix Mackenziana Pliyllodoce glandulifera 



exigua Menziesia ferruginea 



" Scouleriana Kalmia poli folia 



glaucops Cassiope Mertensiana 



Bet ula fontinalis Gaultheria humifusa 



Odostemou Aqui folium Vaccinium mcmbranaceum 



Rub us parviflorus " oreophilum 



Amelanchier alnifolia scoparium 



Crataegus Douglasii Artemisia cam,porum 



Prunus demissa frigida 



Pachystima Myrsinites cana 



RJius Rijdbergii 



The following 1 species seem to have entered from the south- 

 ern Rockies or the Great Basin : 

 Yucca glauca Opnntia polyacantha 



Atriplex truncata Mammillaria missouriensis 



Sarcobatus vermiculatus vivipara 



Eurotia lanata Gilia pun gens 



Grayia spinosa Sambucus glauca 



Ribes aureum Aplopappus suffruticosus 



Rosa Fendleri Tetradymia canescens 



" ultramontana spinosa 



Cercocarpus ledifolius ChrysotJiamnus nauscosus 



montanus viscidiflorus 



Purshia tridentata Artemisia tridcntata 



Amelanchier oreophila spinescens 



" utaJiensis 



Yucca is a common plant in many localities on the plains 

 of eastern Montana. It is usually found on the slopes of the 

 foothills or benches. On the other hand Opuntia .polyacantha, 

 also plentiful in the same region, is more abundant on the low 

 flat benches. The most interesting species in the above list is 

 the mountain mahogany, Cercocarpus ledifolius, which is found 

 as far north in the Rocky Mountains as Helena. It is plentiful 

 about the head of the Bitter Root Valley where it has apparently 

 arrived from the hills of southern Idaho across the Bitter Root 

 Range. Purshia probably came from the same source but is 

 somew r hat more widely distributed through the Bitter Root Val- 

 ley and sparsely farther north in the Flathead Valleys and 



