4o8 George E. Nichols, 



the climatic mesophytic forest of this district." Krummholz 

 differs from forest scrub not only in the lesser height of the 

 trees, and in their more pronounced tendency to approximate the 

 Krummholz growth fomi, but in the lesser abundance of the 

 balsam fir. 



Factors responsible for failure of forests to develop. — True 

 alpine conditions are found nowhere in northern Cape Breton. 

 This is evidenced by the complete absence of an arctic-alpine 

 flora. On Mount Franey, the highest measured mountain in 

 Nova Scotia, for example, no species were observed which are 

 not equally abundant at lower elevations, while with the excep- 

 tion of perhaps a few forms such as Betiila pumila, Vaccinium 

 uliginosum, and V. pennsylvanicum angustifolium, the flora of 

 the interior plateau scarcely differs in its composition from that 

 of the upper mountain slopes. The general failure of forests to 

 develop in the barrens can be ascribed very largely if not wholly 

 to edaphic factors, especially to the combined influence of snow 

 and wind during the winter months. Heavy winds prevail on 

 the barrens intermittently at all seasons, but particularly in 

 winter. The primary effect of the wind at this season is to 

 sweep the snow from the more exposed sites and pile it up in 

 the more sheltered situations. Exposed hill crests may be swept 

 entirely bare, while in some of the ravines great drifts fully fifty 

 feet in depth may accumulate. In general, it is apparent that the 

 height of the trees, with the possible exception of the tamarack, 

 is closely correlated with the depth of the snow in winter. In 

 exposed situations any branches which project above the surface 

 of the snow are liable to be killed by excessive transpiration or 

 through the sand-blast-like action of the wind-driven snow. 

 Individual shoots may survive a few mild winters, but then 

 comes a severe winter and they too are killed. In the case of 

 forest scrub, an association-type to be described presently, it is 

 evident that, in spite of the apparently exposed position of the 

 low hills on which it is commonly developed, local conditions 

 favor the accumulation of snow drifts in much the same manner 

 that sand dunes are built up along the seacoast. 



Age of dwarf trees. — -In this connection, a few observations 

 regarding the ages of some of the dwarf trees may be of interest. 

 The tamarack shown in Fig. 56, situated near the crest of the hill 

 pictured in Fig. 51, was found to have more than 150 annual 



