THE SUMMITS 161 



forest, but of limited tracts of even though usually not dense 

 stands, or more often of bunched trees in small groups, separated 

 by meadows, bogs, lakes, rock fields, snow fields, chasms, etc. 

 Snow is perennial only in small patches, and even the glaciers 

 of the northern part are of very limited extent. The growing 

 season is short, however, and at an altitude of 6,000 feet may be 

 limited to about two months or less during July and August. 

 Heavy frosts usually occur and snow may fall during this time. 

 Small brooks fed by melting snow run low or cease to flow at 

 night and the days are usually long and bright and warm. "Veg- 

 etation awakens quickly and advances rapidly to flowering, 

 fruition and rest, so that usually before the end of August fresh 

 snows have begun to mantle the peaks and higher ridges. 



The Rocky Mountains of Montana have no summer snow 

 line, and in rare cases only a distinct timber line. Most of the 

 high mountains are clothed with trees of fair size almost to their 

 very summits, especially on their more sheltered slopes, and 

 where forests are lacking, the influence is not snow nor cold but 

 chiefly wind and desiccation. Mt. Lolo of the Bitter Root Range, 

 rising to about 9,000 feet, is forested practically to its summit, 

 and Trapper Peak, the highest point of the same range, reaching 

 10,175 feet, is likewise timbered nearly tx) the summit. At Gib- 

 bon's Pass across the Continental Divide from the Bitter Root 

 to the Big Hole the road passes through a dense forest of lodge- 

 pole pine, and where the railway lines cross the divide are scat- 

 tering stands of pine and .juniper. The peaks and high ridges 

 of Glacier Park, from 6,000 to 10,000 feet have no perceptible 

 timber line. 



Under the conditions cf the very short growing season and 

 other adverse aspects of such situations it is inevitable that the 

 increment of woody plants from season to season should be very 

 small, especially in the cases of trees in situations at all exposed 

 to wind. Trees sheltered in the center of a group make fairly 

 rapid growth. Near the top of the Swan Range a small tree 

 (Abies lasiocarpa) about 6 feet in height and about 3 inches 

 in diameter at the ground stood at the edge of a group, but in a 

 .sheltered basin with trees back of it rising 40 feet or more. This 

 tree had no limbs on its windward side but to the leeward ex- 

 tended its branches about two feet. A section across the stem 



