154 



BOTANICAL GAZETTE 



[SEPTEMBER 



*k 



Fig. i. — Map of southern Rocky 

 Mountains, except westernmost ranges; 

 mountain areas shaded; names of areas 

 indicated by numbers are: i, Laramie 

 Mountains; 2, Medicine Bow Range; 3, 

 low mountain area connecting Laramie 

 and Front ranges; 4, foothills of Poudrc 

 River area; 5, Front Range; 6, Rampart 

 Range; 7, Pike's Peak highland; 8, Park 

 Range; 9, Saguache Range; 10, Upper 

 Arkansas Valley (between 9 and 8); 

 11, low mountains; 12, Wet Mountain 

 Valley; 13, Sangre de Cristo Range; 14, 

 Wet and Greenhorn mountains; 15, 

 Huerfano Park; 16, southern sedimentary 

 plateau; 17, Culebra Range; 18, Spanish 

 Peaks highland; 19, Raton mesas. 



While in general the plains 

 and mountains contrast rather 

 sharply at their junction, this 

 is not always true; the moun- 

 tain-front is a transition zone 

 in places a number of miles 

 broad rather than a line. It is 

 not determined alone by alti- 

 tude, by topography, by char- 

 acter of the bedrock, or by 

 climate; it is the resultant of 

 all of these. For the sake of 

 clearness the foothills may be 

 described as the drier and less 

 elevated (about 5800-8000 ft.) 

 part of the mountain plateau, 

 with vegetation composed of 

 grassland, scattered rock pines, 

 and a few other trees (foothill 

 zone, Ramaley 8). Except in 

 the southern " sedimentary pla- 

 teau" (fig. i), perhaps rather 

 to be considered part of the 

 mountain-front area, the foot- 

 hills may be said to comprise the 

 granitic hills of the mountain- 

 mass proper; while to the 

 mountain-front zone may be 

 assigned the upturned sedimen- 

 tary hogbacks and longitudinal 

 valleys, sedimentary outcrops, 

 buttes and broken plateaus, and 

 the mesas and upper parts of 

 the debris-covered slope to the 

 plains. The vegetation is of the 

 greatest variety. The plains 

 proper may be said to com- 

 mence where the mixed soil and 



