vil] MOORLAND ASSOCIATIONS 193 
Susp-ALPINE GRASSLAND 
In the end, the retrogressive changes outlined above result 
in the complete disappearance of the peat; and on the surface 
thus laid bare, a new set of species begins to invade. In this 
invasion the ordinary inhabitants of the surrounding peat- 
moors can take no part; and the successful invaders are the 
more hardy members of the Nardus grassland. As has been 
stated (see page 185), such plants follow the streams of the 
peat-moors almost to their sources; and hence they are the 
plants which one would expect to be the first to establish 
themselves in the newly formed habitat. The summit of 
Bleaklow Hill, four miles north of the Peak, is tenanted by 
an open plant association which has almost certainly originated 
in the way just described. On the summit of Great Whernside 
and other hills of the mid-Pennines, Smith and Rankin describe 
an association which seems to be capable of a similar interpre- 
tation: “the summit-ridge from the edge of the peat-bog 
upwards is rocky, with a scanty soil which supports a meagre 
vegetation consisting of grasses. Here and there are patches 
or islands of peat” (Smith and Rankin, 1903: 154). 
The following species were observed on the summit of 
Bleaklow Hill :— 
Nardus stricta Rumex <Acetosella 
Deschampsia flexuosa Potentilla erecta 
Festuca ovina (=P. Tormentilla) 
Agrostis vulgaris Calluna vulgaris 
Juncus squarrosus Vaccinium Myrtillus 
Luzula erecta Galium saxatile 
On Great Whernside, Smith and Rankin (loc. cit.) record 
Festuca ovina forma vivipara and Poa alpina; and it is not 
impossible that a careful search on Bleaklow Hill would reveal 
these plants, although they have not yet been recorded for 
Derbyshire. 
The case of this sub-Alpine Pasture illustrates the im- 
portant principle that a succession of plant associations, once 
initiated, may lead from one plant formation to another (cf. Moss, 
19106: 37). In the case under discussion, the retrogressive 
succession began in the closed cotton-grass association, continued 
M. 13 
