VIl] MOORLAND ASSOCIATIONS 179 



heather (which has no underground buds) has been completely 

 killed. Deschampsia flexuosa and Nardus stricta are also fre- 

 quently conspicuous during the first summer after the firing, 

 doubtless owing to invasion by seed. As a rule, seedlings of 

 heather establish themselves immediately and in abundance 

 after firing; and, when this occurs, the complete and speedy 

 rejuvenation of the heather moor is assured. The repopulating 

 of the moor by heather is due to the germination of its minute 

 seeds which are blown from adjoining heather-clad tracts. This 

 fact is known to the keepers who therefore do not fire large, 

 continuous areas in any given year. Seedlings of heather 

 (Calluna vulgaris) may be found in abundance in places where 

 the moor was burned during the previous year. 



Typical dry heath, which is characteristically developed on 

 sandy soils throughout the lowlands of England and especially 

 so in the south and east, does not occur on the Pennines. 

 Graebner (1901) has shown that this association does not in 

 North Germany occur in localities where the rainfall is below 

 28 inches (71 cms.); and it would also appear, judging from its 

 distribution in England, not to be developed where the mean 

 annual rainfall is above 35 inches (89 cms.). 



The following species occur in the less wet, that is, the 

 typical parts of the heather moors of the southern Pennines: — 



Dominant 

 Calluna vulgaris 



^ Locally sub-dominant 



Erica cinerea Vaccinium Myrtillus 



Locally abundant 



Polytrichum spp. Vaccinium Vitis-idaea 



Pteris aquilina Galium saxatile 



Ulex Gallii Deschampsia flexuosa 



EmpetrvuB nigrum Juncus squarrosus 



12-2 



