AS A HOME FOR BUTTERFLIES 83 



ceding, but at present receives no side-light from 

 the west. 



One will hardly fail to notice that while the 

 forest line at the White Mountains is tolerably 

 well marked (at a height of about 4000 or 4500 

 feet), it is always succeeded above by a consider- 

 able area, where the dwarfed spruce or " scrub, " 

 strugglmg upward with ever diminishing height, 

 conceals the gray rocks in a covering of uniform 

 green, excepting on the unstable surfaces of the 

 steeper slopes, — an area which is strongly contrasted 

 with the barren gray broken rocks above, which lie 

 piled in vast heaps exposed to fidl view, except 

 where a patch of sedge furnishes a small and bar- 

 ren pasture upon some more favored plateau. The 

 sides of these mountains, where they rise to their 

 highest culmination, are thus divisible into a forest 

 and an alpine region, and the latter into a lower, or 

 scrub, and an upper, or rocky, district. These two 

 subdivisions of the alpine region correspond fairly 

 well with the areas occupied by the two mountain 

 butterflies just mentioned. There is no doubt that 

 occasional individuals of the White Mountain but- 

 terfly (Oeneis semidea) will be found far within 

 the limits of the lower alpine region ; for the fierce 

 blasts of wind which sweep around these lofty ele- 



