750 GEOLOGICAL SURVEY OF THE TEREITORIES. 



ently delicate plants were seen blooming through the snow, and vegeta- 

 tion, though limited in species, seems abundant until within three hun- 

 dred feet of the summit of Mount Hayden, where all plant-life ceases, 

 except a few lichens clinging to a bare rock, which is swept continually 

 by fierce winds. A fine field was presented here for the collection of 

 truly alpine plants, and no opportunity was lost for obtaining anything 

 peculiar to this great elevation, unusually exposed, as it is, to tempests. 

 All the alpine plants are noted in the catalogue, and the elevations 

 given at which they were collected. The Teton Eange is heavily tim- 

 bered with Coniferw, chiefly Finns ponderosa^ to an altitude of 11,000 

 feet, this being the average timber-line of the whole range. The maxi- 

 mum growth is at an altitude between 8,000 and 10,000 feet. A marked 

 difference is observed, however, between the western and eastern slopes, 

 the latter being much more densely timbered than the former, and the 

 trees much larger and less twisted and gnarled. This seems to result 

 from the fact that on the eastern side the Tetons rise almost sheer out 

 of the plains, presenting an enormous perpendicular wall, behind which 

 the trees of the eastern slope are completely sheltered; while, on the 

 west, the peaks are rounded down into the plains by the foot-hills, and 

 this whole, broad, sloping side is exposed to every blast from the north 

 and west. 



One noticeable feature in the tree-life on the mountains is the abrupt- 

 ness with which it terminates at the average height of 11,000 feet. Tall, 

 straight Coniferw are seen growing to the very edge of this line, and 

 one step takes us from a forest to a bleak, open waste, where not a tree 

 can live, except a few stunted and twisted forms that have been bent 

 out of all shape by the superincumbent mass of snow that rests upon 

 them during the winter. These stunted forms, sometimes even with 

 their tops matted close to the ground, are always found growing behind 

 some wall of rock or steep bank, where the winter snows accumulate in 

 immense drifts and completely cover and protect them during the blight- 

 ing winters of that high altitude. According to Parry "the so-called 

 timber-line marks the extreme i^oint of minimum winter temperature, 

 below which no exposed phsenogamous vegetation can exist." All life 

 above this limit is buried by the deep winter snows, and thus protected ; 

 heiice in this truly alpine region many plants are found that are com- 

 mon at much lower altitudes. The flowering season is necessarily short, 

 and we were fortunate in being upon the Tetons in the very midst of it, 

 during the last part of July. 



I have said that all phgenogamous life ceases within 300 feet of the sum- 

 mit of Mount Hayden, which isabout 13,800 feet above the level of the sea. 

 This is owing to the great sharpness of the peak not allowing the 

 snow to rest upon it, but to accumulate in great banks upon its lower 

 slopes. Hence there is no protection for plants during the long winters 

 above this bank, and we pass suddenly from a bright, varied alpine 

 vegetation to bleak, lichen-covered rocks, just as, 2,000 feet below, we 

 passed suddenly from forest growth to a low, matted vegetation. It is 

 noticeable that the timber-line becomes lower as we advance farther 

 north in almost a fixed proportion to the latitude. The altitude of this 

 line was accurately measured by Mr. Henry Gannett upon every mount- 

 ain he ascended, and I insert below a table containing the altitude of 

 this line upon several peaks, together with their approximate latitudes. 

 We were unfortunate in obtaining no accurate measurement upon the 

 Tetons, and hence the altitude of the timber-line upon this isolated 

 range is but approximate. 



The timber-lines in Colorado are mostly from Parry's measurements. 



