566 
Erigeron lanatus Hook. 
eum (Sieversia) Rossii R. Br. 
Kalmia glauca var. microphylla 
Hook. (= K. microphylla 
Hook.). 
Mertensia alpina Torr. 
Part IV. Chapter 3. 
Eritrichium (Omphalodes) Ho- 
wardi A. Gr. 
Orthocarpus pilosus Wats 
(= Castilleja pilosa Wats. 
Pedieularis Parryi A. Gray. 
Primula Parryi A. Gray. 
. 
. 
20 
Ranunculus Eschscholtzü 
Schlecht. 
Calandrinia pygmaea A. Gray 
(= Oreobroma Grayi Britt.). 
Silene acaulis L 
Salix chlorophylia Anders. 
Myosotis sylvatica var. alpestris Anemone nareissiflora L. » glauca L, var. villosa, 
Koch (=M.alpestrisSchmidt). 
The alpine and subalpine 
floras of the Western slope of Rocky Mountains in southwestern 
Colorado are at this southern latitude almost the same as those of northern Colorad 
o. Pachystima 
myrsinites, Erythronium grandiflorum are common. Aquilegia canadensis takes the place of A. 
caerulea found with such northern ones as Calypso borealis, Listera cordata, Nephrodium (Aspidium) 
filix-mas. ; 
c) Black Hills Area. 
The flora of the Black Hills of South Dakota is varied. This is due to 
their phytogeographic location (see page 107) which is midway between the 
coniferous forest around the Great Lakes, the deciduous forest vegetation of 
the east and the Rocky Mountain vegetation, while in addition they are surroun- 
ded by the vegetation of the prairies and the great plains (see colored map). 
It consists of plants from the east (see page 240), from the Saskatchewan region, 
from the prairies and table-lands west of the Missouri River, from the Rocky 
Mountains and from the region west thereof. In the foothills and the lower 
part of the Black Hills the flora is essentially the same as the plains in the 
midst of which these mountains are found. The more elevated portions have 
a vegetation of more northern origin. Some plants belong to the Rocky 
Mountains; among them two trees Pinus fonderosa var. scopulorum and 
Betula occidentalis, the rest of the plants are eastern or transcontinental. The 
flora of the lower parts of the district resembles, therefore, more the flora of 
the Interlacustrine Area than that of the Rocky Mountain Region. The 
foothills and surrounding plains may be omitted from consideration, because 
the vegetation is essentially that peculiar to the high dry plains of Nebraska, 
Wyoming and neighboring States. The really mountainous parts of the Black 
Hills which are related topographically and in part floristically to the Rocky 
Mountains is the Harney Range. The principal tree is the Rocky Mountain 
yellow pine Pinus ponderosa var. scopulorum, which is the only tree that 
makes a forest. As this tree forms the principal facies, the district has : 
been placed in the classification as a part of the Rocky Mountain Region. 
On the north side of the mountains is the northern white spruce Picea alba 
(= P. canadensis). It must have come into the district when the climate was 
much colder than now. 
Of the deeiduous trees there are: Betula papyrifera, B. oceidentalis, Populus tremuloides, 1 
Salix Bebbiana (= S. rostrata), S. discolor, S. cordata, while down along Squaw Creek oceur 
Quercus macrocarpa, Ulmus americana. hrubby plants are Amelanchier alnifolia, Cornus 
stolonifera, Corylus rostrata, Neillia opulifolia, Ribes setosum, Ribes oxyacanthoides, R. cereum, 
R. lacustre, Shepherdia canadensis, The following Rocky Mountain plants occur in the 
I VS ER ER he Dog 
ae ae En re 
53 
TTS, 
a 
