entire southern part of the State at this time. Beyond, to the 

 south, lay a wide belt of the white pine, and in turn beyond it 

 came the deciduous forest. Encroachment of one zone upon 

 another above has been continuous, societies gradually ascending, 

 resulting in the present distribution of plant societies upon the 

 mountain. It is obvious that this encroachment was one of hori- 

 zontal zonation but for any one place it is a story of vertical 

 succession. This progression will be considered in the section 

 upon plant societies. 



The place where this isolated Arctic flora first encroached upon 

 the mountain is an interesting point of conjecture. From the 

 retarding effect of the basin glaciers, the very favorable oppor- 

 tunity on the gentler incline of the stoss side of the mountain, 

 and the greater sun exposure, it would seem probable that the 

 first advance was from the southwest and west. This idea would 

 seem to be confirmed in the present distribution of the spruce 

 and fir. Their higher ascent on this side, their apparently 

 greater age on the south and west slopes, and the advance of the 

 Krummholz from this section, all indicate more favorable con- 

 ditions, past and present, on this part of the mountain. As to 

 the east side of the mountain, and in particular the basins, it 

 seems very evident, from the present conditions, that the Great 

 basin was the first to be claimed by the plant migrants, and that 

 the North basin (Fig. i) resisted this encroachment for a much 

 longer time. In fact, presenting as it does a desolation simu- 

 lated only on the highest slopes, it would seem that the disap- 

 pearance of the valley glacier from this basin was comparatively 

 recent. 



V. FACTORS. 



If a bird's eye view be taken from the summit of the mountain 

 a varied panoramic picture greets the eye. A vast forest, 

 coniferous in places, deciduous in others, dotted here and there 

 by sphagnum bogs and a multitude of lakes whose shores are 

 fringed with meadows, extends for miles, an unbroken landscape 

 feature. If the mountain is now considered in particular, one 

 sees in contrast, bare exposed rocks, mats of appressed 

 growth, scrubby forest forms, and alpestrine meadows. That 

 there are at least two distinct sets of causes operating in this 

 region is very obvious. One determines the general plant physi- 



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