NEW VOkK 



BOTAiNICAL 



OAkOEM 



TORREYA 



Vol. 26 No. 6 



November-December, 1926 



BOTANY OF THE MONTANA ROCKIES 



J. E. KiRKWOOD 



The wide topographic diversity of Montana is reflected in the 

 varied forms of its plant life. Its high mountains, deep canyons, 

 broad valleys and open plains provide the settings for a display of 

 floral compositions lending charm and interest to its landscapes. 

 As one travels westward over the wide plains of eastern Montana 

 he views from the car window great rolling ranges of grassland 

 through which the courses of streams are marked by lines of 

 cottonwoods and willows. Along the breaks between the benches 

 and the river bottoms are scattered pines and junipers, the out- 

 posts of the coniferous forests darkening the slopes of distant 

 mountains which appear first in isolated peaks like sentinels 

 guarding the approach to the summit of the continent. In the 

 more arid localities the grasses thin out and patches of sage 

 appear. If in June, one may see stalks of the Spanish bayonet 

 covered with white flowers and the yellow blossoms of the low 

 prickly pear. Both the Yucca and the cactus are the northern- 

 most representatives of their kind, but are widely distributed 

 over the plains and foothills adjacent to the Rocky Mountains. 



The annual rainfall lessens with the distance westward until 

 the ascent of the mountains begins when it increases, owing to 

 greater altitudes. This accounts for the appearance of forests 

 which begin to cover the slopes and ridges. Throughout the 

 Rocky Mountains coniferous forests abound especially at eleva- 

 tions above 5000 feet. Below this level the effect of diminished 

 precipitation is seen in the occurrence of grasslands especially 

 on southern exposures, while on the northern slopes the forests 

 extend into the valleys. These forests reach far to the north- 

 west into British Columbia and Alaska, thence southward along 

 the Cascade and Coast Ranges to California. 



105 



