162 The Plant World. 



of the Rockies. This striking plant produces a large perennial 

 root. It seems to defy any amount of dry weather. One is in- 

 terested also in the Cactaceae found in the eastern plains. The 

 Opuntias like O. Rafinesquii are common on the plains of Denver, 

 and the same is true of the O. missouriensis and the prickly red- 

 flowered O. rhodantha. One is interested in seeing for the first 

 time as one passes along the line of the D. & R. G. R.R., in the 

 vicinity of Pueblo, the small tree-like O. arborescens. 



The conifers of the Rocky Mountains and the Pacific Coast 

 are the most characteristic features of the region. The species 

 are fairly numerous. In the lower altitudes on the east slope of 

 the Rockies the bull pine {Pinus ponderosa) is abundant but 

 occurring more or less in scattered groves and here and there in 

 canyons and draws; or on the slopes of the mountains is the 

 Juniperus scopulorum), while in the northern regions in Canada 

 is the red cedar /. virginiana). On the west slope of the moun- 

 tains is the western red cedar (/. occidentalis) and the variety 

 monospcrma) ; on the south side of the Uintah Mountains it forms 

 a well marked zone, especially abundant on the limestone shale. 

 The undergrowth here consists almost entirely of a few vernal 

 blooming plants and a few hardy shrubs like Rhus canadensis 

 var. trilobata and in the canyons the Amelanchier alnifolia. 



The zonal distribution of these conifers is certainly well 

 marked in many ranges. The Douglass fir {Pseiidotsuga 

 Douqlasii) is common everywhere in the canyons above 6,000- 

 7,000 feet, in the front Rockies, in the San Miguel region as well 

 as in the Uintah and Bitter Root Mountains. In the latter 

 mountains it hardly extends beyond 8,000 feet, while in the Wa- 

 satch Mountains I have found it close to 10,000 feet. In Colo- 

 rado the zonal distribution is something like this, first the Pinics 

 ponderosa and Juniperus scopulorum, then the Douglass fir and 

 black fir {Abies concolor), sometimes associated with the A. 

 lasiocarpa. The Colorado blue spruce {Picea Parryana) extends 

 much lower down than the Douglas fir and in the Uintah IMoun- 

 tains occurs in marshes and swamps from 6,500 feet to 8,500 feet, 

 but of course at a much lower altitude on the Pacific Coast and 

 in Montana, in southern Colorado followed by the Pinon pine 

 {Pinus edulis) then Pinus ponderosa at an altitude of 8,000 feet, 

 where it occupies the mesas and slopes and beyond the lodge 



