Vegetation of Northern Cape Breton. 405 



importance. In its typical development, then, the writer would 

 regard this type of association as a true heath. ^* 



Transition from heath to Krummholz. — All intergradations 

 are found between typical dwarf shrub-spruce heath and 

 Krimimholz, the association-type to be treated next, and in this 

 connection the behavior and ecological relations of the spruce 

 and other evergreen conifers has an important bearing. As the 

 principal species concerned, the black spruce will serve to illus- 

 trate the points in question. Like the ericaceous shrubs, this 

 species appears at an early stage in the development of the heath : 

 it is antecedent wath reference to the hummocks. Through the 

 death of the primary leader, the extensive development and 

 copious branching of the lateral shoots, and commonly also 

 through vegetative reproduction by layering, it characteristically 

 assumes a low, compact, rounded, shrub-like habit. So closely 

 may one of these bushy spruces conform with the contour of the 

 hummock alongside which it grows that on superficial examina- 

 tion it appears to be growing on the hummock itself ; but 

 ordinarily the relationship is very different. For the shade pro- 

 duced by these clumps of spruce has an important local effect 

 on the nature of the vegetation, in that it inhibits the growth 

 of lichens and thereby prevents or checks hummock formation. 

 In some areas the depressions between adjacent hummocks are 

 completely filled in by a dense snarl of scrubby spruces which 

 rise to about the same general level as the low vegetation which 

 tops the hummocks. From a distance the surface contour of 



"Warming ('09, p. 210) defines heath as "A treeless tract that is 

 mainly occupied by evergreen, slow-growing, small-leaved dwarf-shrubs 

 and creeping shrubs which are largely Ericaceae." But the use of the 

 term is not wholly restricted to such areas. Warming himself recognizes 

 lichen-heath and moss-heath (op. c, pp. 205, 208), and Graebner ('01, 

 pp. 26, 27), while distinguishing as most representative areas of the sort 

 specified by Warming, extends the term to include "not only areas domi- 

 nated by ericaceous shrubs, but open tracts in which there is neither a 

 good tree growth nor a close grass turf; [in which] ligneous plants 

 dominate, especially low shrubs. [Thus,] what we call pine or oak bar- 

 rens would probably be included in Graebner's heath" (quotation from 

 Cowles' review of Graebner's book). Applying the term in this latter 

 sense, Harshberger ('11, pp. 165-168) regards the "plains" of the New 

 Jersey pine-barrens as heath. Riibel ('14, p. 237) would restrict the 

 use of the term heath to "ericoid-leaved bushland." ' 



