Vegetation of Northern Cape Breton. 391 



to the fact that ahiiost invariably they are heart rotted. It is 

 a noteworthy fact, as Cooper ('13, pp. 17-21) has pointed out, 

 that while the balsam fir far outnumbers all other trees in the 

 forest, yet, owing to its susceptibility to fungus attack and 

 consequent liability to windfall, its relative abundance decreases 

 greatly with age. In other words, "its high birth-rate is 

 balanced by a high rate of mortality." 



Second in importance to the balsam fir in the climax forest is 

 the white spruce, which is well distributed throughout, com- 

 mon, yet nowhere approaching the balsam in abundance, and 

 conspicuous by reason of its relatively large size. It ordinarily 

 attains a diameter of sixteen inches, sometimes of more than 

 two feet, and as a rule is correspondingly taller than the balsam. 

 Black spruce is also an important constituent, locally quite 

 common, and in size about equal to the balsam. It never attains 

 here the proportions which it exhibits in the Adirondacks where, 

 in virgin forests, trees three feet in diameter and more than a 

 hundred feet high are frequent. These three trees comprise 

 the evergreen coniferous element in the climax forest. The 

 deciduous element is represented primarily by two species, the 

 paper birch and the mountain ash. The paper birch is well 

 scattered through the forest, somewhat less abundant, perhaps, 

 than the white spruce, but prominent by reason of its showy 

 bark and spreading, broad-leaved crown. In height it seldom 

 exceeds the average for the forest as a whole, and its trunk is 

 rarely as much as a foot in diameter. The mountain ash is a 

 very characteristic and omnipresent constituent, usually a small 

 undertree, but sometimes fully fifty feet high with a trunk a foot 

 in diameter. The yellow birch, though frequently represented 

 in favorable situations, never reaches anywhere near the size 

 which it attains in the lowland. Red maple is more or less 

 scattered throughout, but as a rule is little more than an under- 

 shrub. The small-toothed aspen {Populns tremuloides) also is 

 occasionally present. 



The undergrozvth in the climax forest. — Below is given a list 

 of the characteristic shrubs and herbaceous vascular plants in 

 the coniferous climax forest. Their general occurrence and 

 local abundance when present is indicated by symbols, as 

 explained elsewhere (p. 283). 



