VII] MOORLAND ASSOCIATIONS 177 



Longdendale are, except at the extreme west, destitute of heather 

 moors; but the main western Calluna mass runs along the 

 southern slopes of the dale for six miles, as far as Woodhead. 

 The most westerly outlier of the heather moors of the Pennines 

 in this latitude occurs at Bakestone moor one mile to the west 

 of the boundary of the district. On the Yorkshire slopes of 

 the hills, beginning at Dunford Bridge, the eastern system of 

 heather moors extends in a general south-easterly direction for 

 about sixteen miles, and is continued eastwards of the present 

 area on to the Sheffield map, no botanical survey of which has 

 been completed. The central system of heather moors occupies 

 a region in the upper portions of the valleys formed by the 

 rivers Derwent and Westend. The eastern heather moors are 

 about three miles broad on the average, and the western about 

 one mile broad. This is a response by the vegetation to the 

 well-known physiographical fact that the eastern slopes of the 

 Pennines descend more gradually into the plain than the 

 westerly slopes. The local altitudinal limit of the association, 

 at about 1500 to 1550 feet (457 to 472 m.), is partly a response to 

 the severer climatic conditions of the higher and more exposed 

 summits, and partly to the wetter soil conditions which obtain 

 on the deeper peat of the higher moors. The latter fact is doubt- 

 less related in part to the higher rainfall and more frequent 

 mists which occur in these regions. It need scarcely be stated 

 that the upper limit of the moorland association of Calluna vul- 

 garis in no way corresponds with the upper limit of the species, 

 which, as a matter of fact, ascends to over 2000 feet (610 m.) 

 in this district (e.g., on Bleaklow Hill); whilst in Scotland 

 (Hooker, 1884) the species ascends to 3500 feet (1067 m.). 



Many outliers or detached areas of heather moors occur, and 

 are interesting as pointing to a former greater extension of the 

 region of heather moors, a region which has been greatly re- 

 stricted by reclamation and conversion into farmland. The 

 sides of the roads and lanes in such reclaimed areas are fre- 

 quently tenanted by moorland plants, such as Calluna, vidgaris, 

 Vaccinium Myrtillus, and Deschampsia flexuosa. 



The western Pennines in the north of the Glossop district 

 are remarkably destitute of heather moors : this is partly due 

 to the fact that the slopes of the hills in that locality are very 

 steep and shaly. 



12 



