171] FLORA OF BOULDER, COLORADO 23 



Aralia nudicaulis Mertensia lanceolata 



Svida stolonifera Dracocephalum parviflorum 



Sanicula Marilandica Mimulus Hallii 



Osmorrhiza longistylis Veronica Americana 



O. obtusa Galium Vaillantii 



Ligusticum Porteri G. boreale 



Heracleum lanatum G. flaviflorum 



Steironema ciliatum Viburnum Lentago 



Collomia linearis Ambrosia trifida 



Hydrophyllum Fendleri Eupatorium maculatum 

 Macrocalyx Nyctelea 



C. SUBMONTANAE 



The Foot-hill Flora covers not only the true foot-hills of 

 the sandstone crags, but also the lower part of the mountain 

 plateau. The flora is rich but monotonous. In most places the 

 vegetation is thin; it is mainly a forest, but the trees are 

 strewn but sparsely over the steep slopes. The amount of 

 naked rock is very great. The altitude ranges from 5,800 to 

 8,600 feet. Some of the main streams, such as Boulder creek, 

 have cut down to about 5,500 feet. Directly west of Boulder, 

 and lying between Boulder and Gregory Canons, is Flagstaff 

 Hill with an altitude of about 6,500 feet. Southwest of Boulder 

 is Green Mountain, lying between Gregory and Bear Canons 

 and having an altitude of 8,100 feet. South of Green Moun- 

 tain is Bear Mountain, which attains a height of 8,600 feet, 

 and is the loftiest peak in the first range of foot-hills in the 

 vicinity of Boulder. 



The Foot-hill Flora merges rather abruptly into that of the 

 mesas at the foot of the crags, and melts insensibly into the 

 Subalpine Flora as it approaches the Main Range. It reaches 

 its maximum development between an altitude of 6,500 and 



