434 RYDBERG: PHYTOGEOGRAPHICAL NOTES 
Comtoserenin scopulorum Adoxa moschatellina 
coloradense Valeriana ovata 
Androsace pinetorum Senecio amplectans 
- Castilleja confusa _ 
Restricted to the Northern Rockies 
Shrubs 
Ribes laxiflorum _ Chiogenes hispudula 
“ hudsonianum Vaccinium occidentale 
“  petiolare . globulare 
Azaliastrum albiflorum Linnaea longifiora 
Gaultheria ovatifolia 
Herbs 
' tAlsine borealis tOzomelis trifida 
Aquilegia columbiana Atelophragma Forwoodii 
: formosa Aragallus foliolosus 
Dentaria rupicola TtOsmorrhiza Leibergii 
Parnassia palustris Ligusticum filicinum 
e Kotzebuei '  Moneses reticulata 
Heuchera glabra . Pyrola uliginosa 
{Pectianthia Breweri ; Aster meritus 
2. PINE SLOPES 
The characteristic tree of this formation in the Southern 
Rockies is the bristle-cone pine, Pinus aristata, which occupies dry 
slopes and ridges especially on the southern side of the mountains. 
It seldom forms a dense forest. Occasionally Picea Engelmannii 
or Populus tremuloides has encroached on the pine slopes and then — 
the woods are more dense. In the lower part of the zone the 
bristle-cone pine is often mixed with the limber pine, Pinus flexilis. 
As Pinus aristata seldom makes a close stand but grows scattered 
on the slopes, the undergrowth is mostly made up of the grass 
formations, either that of the mountain slopes or that of the hog- 
backs. . Wherever the trees stand close the undergrowth contains 
more and more of the element found in the more open woods. 
Some of the more common species are: Arenaria Fendleri, Arnica 
cordifolia, A. pumila, A. Parryi, Polemonium delicatum, Draba 
streptocarpa, D. auretformis, Pseudocymopterus montanus, Solidago 
