106 VEGETATION OF THE PEAK DISTRICT [CH. 



I. Grassland of the Sandstones and Shales: 

 Siliceous Grassland 



Two types of siliceous grassland have been described in 

 previous botanical surveys of the Pennines (Smith and Moss, 

 1908 : 384 ; Smith and Rankin, 1903 : 158 ; Lewis 1904 a : 323, 

 1904 6: 275),. and have been distinguished as wet and dry. 

 The most abundant and characteristic grass of the drier type 

 of siliceous grassland is the mat-grass {Nardus stricta) and 

 that of the wetter type is the purple moor-grass (Molinia 

 caerulea) (cf figure 14). The two species are respectively 

 dominant in the two associations since they nearly monopolize 

 the ground and form the great bulk of the turf, the asso- 

 ciated species being therefore more or less controlled by them. 

 The former association may therefore be termed Nardus grass- 

 land (Nardetum strictae) and the latter Molinia grassland 

 (Molinietum caeruieae). To some extent, the associations are 

 layered plant communities; and the smaller plants receive a 

 certain amount of shade and shelter from the dominant ones. 

 As is usual in plant associations, one or another of the 

 dependent species occasionally becomes more or less social; 

 and thus plant societies and facies arise. 



(1) Nardus Grassland 



Typical Nardus grassland (see figure 13) occurs on steep 

 shaly slopes of the non-calcareous hills. In summer, this 

 association is characterized by a grassy turf, grey-green in 

 colour, dry and slippery. In late autumn, winter, and early 

 spring, the ground is damp and sodden ; and the bleached 

 haulms of the mat-grass (Nardus stricta) give tone to the 

 landscape, and may be recognised at a considerable distance. 

 The silver hair-grass (Deschampsia flexuosa) is, in this district, 

 a constant associate. In winter, the mat-grass is very much 

 more conspicuous than the hair-grass, as, during this season, 

 the short leaves of the latter are usually more or less hidden 

 beneath the long, white sprays of the dead shoots of the former. 

 Under such conditions, the hair-grass, even though very 

 abundant, is apt to be overlooked. It is only in early summer, 

 when the tall, purple scapes of the hair-grass are in bud, flower. 



