vit] 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 (eg., on Bleaklow Hill); whilst im 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 vulgaris, 
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. 
M. 12 
