Recent History of the Rocky Mountain Flora. 249 
Juniperus nana Willd. to Colorado. 
» virginiana L. to Colorado. 
Kalmia glauca Ait. to Colorado. 
Negundo aceroides Moench (= Acer 
Negundo L.). 
Populus monilifera Ait. (= P. deltoides 
Marsh.). 
»  tremuloides Michx. to Colo- 
rado. 
Prunus americana Marsh. 
» _ pennsylvanica L. to Colorado. 
Rhus glabra L. to Colorado. 
» toxicodendron L. to Colorado. 
Ribes cynosbati L. to Colorado. 
»  floridum L’Her. to Colorado. 
» lacustre Poir. to Colorado. 
Ribes prostratum L’Her. to Colorado. 
Rubus strigosus Michx. to New Mexico. 
Salix amygdaloides Anders. 
» Bebbiana Sarg. (= S. rostrata 
Richardson) to Colorado. 
»  novae-angliae Anders. to Colo- 
rado. 
» phylicifola L. (= 5. chloro- 
phylla) to Colorado. 
» reticulata L. to Colorado. 
Sambucus canadensis 
Symphoricarpos occidentalis Hook. to 
Colorado, 
Vaccinium myrtillus L. to Colorado, 
Utah and northward to Alaska. 
Viburnum pauciflorum Pylai. 
Vitis riparia Michx. to Colorado. 
»  oxyacanthoides L. to Colorado. 
A considerable number of shrubs have taken a northern route from the 
east and northeast across the continent, reaching the Pacific coast and Cali- 
fornia by way of Montana, Idaho and Washington and in some cases migrating 
southward through the Rocky Mountains. These transcontinental shrubs are: 
Amelanchier alnifolia Nutt. Rubus nutkanus Mog. 
Arctostaphylos uva-ursi Spreng. >»  occidentalis L. 
Betula glandulosa Michx. Salix cordata Muhl. 
Corylus rostrata Ait. ' >»  longifolia Muhl. 
Juniperus sabina L. var. procumberss >» rostrata Richards. 
Pursh. ' Sambucus racemosa L. 
Lonicera coerulea Linn.  Shepherdia canadensis Nutt. 
» involucrata Banks. | Spiraea betulifolia Pall. 
Physocarpus opulifolia Maxim. Symphoricarpos racemosa Michx. 
Potentilla fruticosa L. | Vaccinium caespitosum Michx. 
- The central and southern Rocky Mountains harbor a considerable number 
of shrubs and trees which are confined to them, but which have either a 
wide extension north and south, or more restricted northern, central, or southern 
range. Those ligneous plants which extend from Montana to New Mexico 
and Arizona are: 
Acer grandidentatum Nutt. 
Picea Engelmanni Engelm. 
Populus angustifolia James. 
A small element consists of those plants which are confined to the 
central mountains: 
Rosa arkansana Porter. 
Shepherdia argentea Nutt. 
| Picea pungens Engelm. 
| Salix monticola Bebb. 
Fraxinus anomala Torr. 
Rubus deliciosus James. 
