68 OUR NATIONAL PARKS 



contorta, var. Murrayand), with a few patches 

 and sprinklings of Douglas spruce, Engehnann 

 spruce, silver fir {Abies lasiocarpa), Pinus flexi- 

 lis, and a few alders, aspens, and birches. The 

 Douglas spruce is found only on the lowest por- 

 tions, the silver fir on the highest, and the Engel- 

 mann spruce on the dampest places, best defended 

 from fire. Some fine specimens of the flexilis 

 pine are growing on the margins of openings, — 

 wide-branching, sturdy trees, as broad as high, 

 with trunks five feet in diameter, leafy and 

 shady, laden with purple cones and rose-colored 

 flowers. The Engelmann spruce and sub-alpine 

 silver fir are beautiful and notable trees, — 

 tall, spiry, hardy, frost and snow defying, and 

 widely distributed over the West, wherever there 

 is a mountain to climb or a cold moraine slope 

 to cover. But neither of these is a good fire- 

 fighter. With rather thin bark, and scattering 

 their seeds every year as soon as they are ripe, 

 they are quickly driven out of fire-swept re- 

 gions. When the glaciers were melting, these 

 hardy mountaineering trees were probably among 

 the first to arrive on the new moraine soil beds ; 

 but as the plateau became drier and fires began 

 to run, they were driven up the mountains, and 

 into the wet spots and islands where we now find 

 them, leaving nearly all the park to the lodge- 

 pole pine, which, though as thin-skinned as they 

 and as easily killed by fire, takes pains to store 



