THE SUMMITS 159 



its liberal seed production, its capacity for resisting a vigorous 

 climate, Avhere the temperature falls to -60 degrees, high winds, 

 adaptability to various soils but not strict in its demands upon 

 soil moisture. It is thin barked and could easily be injured by 

 fire, but in the open stands where it usually occurs there is less 

 danger from this menace than is usual with other species. It 

 seems not to be especially susceptible to disease. On the other 

 hand its disadvantages in the matter of seeding, the limitations 

 in the facilities for dispersal, the size of the seeds and the eager- 

 ness with which they are sought by animals, and its intolerance 

 of shade militate against its dominance in the range which it 

 occupies. 



The limber pine has an extensive total range from Alberta, 

 southward thrcugh the Rocky Mountains to New Mexico and 

 westward to California. In the Belt Mountains it comprises 

 about 8% of the forest species and about 2% in the Absaroka 

 Range. It mingles more or less with lodgepole pine at the upper 

 limits of distribution of that species and in the higher sub-alpine 

 /r.ne is found with spruce, fir. and whitebark pine. 



THE Sr AIM ITS. 



The sub-alpine zone of the Montana Rockies, as above 

 defined, represents the Hudsonian zone of Merriam and is 

 with reference to all parts of its vegetation, a zone of sur- 

 passing interest. Its tree forms are few, it has a limited num- 

 ber of shrubby species and a considerable number of herbaceous 

 perennials. The trees are Piniis albicaulis, P. flexilis, Larix 

 LijalU, Picea Engelmannii, Tsiiya Mertensiana, Abies lasiocarpa, 

 and Juniperus scopulorum. In shrubby form Juniperus com- 

 mit n is also occurs in abundance. All of these except Lyall's 

 larch and the black hemlock have a distribution extending across 

 the State from north to south, and all except these two and the 

 limber pine are found on both sides of the Continental Divide. 

 Two of them, Picca Engelmannii and Juniperus scopulorum, 

 have a wide range of altitude, from the crest of the divide at 

 6,000 feet or more down to the lowest point in Montana. Larix 

 Lyallii belongs consistently to the high altitudes. 



The aspect of the sub-alpine zone is not that of a continuous 



