Iv] GRASSLAND ASSOCIATIONS 107 
or fruit that this species becomes obtrusively conspicuous; and, 
at such times, it gives the tone and colour to the whole 
association. There seems little doubt, however, that the 
Nardus association of the Peak District is ecologically identical 
with: that of the Wicklow Hills (Pethybridge and Praeger, 
1905: 157) and that of the northern Pennines (Lewis, 1904 a: 
324; 19046: 275), even though the silver hair-grass is not 
included in the lists of these districts. 
The silver hair-grass of the hills of the Peak District 
belongs to the form with short, wiry, and sub-squarrose leaves 
(Deschampsia flexuosa, ? var. montana): the form in the oak and 
birch woods has much longer, more limp, and more slender 
leaves. Woodhead (1906: 383) has described and figured the 
structural differences of some of the forms of this plant. 
The two grasses (Nardus stricta and Deschampsia flexuosa) 
remain co-dominant up to the edge of the moorland plateau, 
which frequently occurs at about 1500 feet (457 m.). Below 
about 1250 feet (381 m.), the common bent-grass (Agrostis 
vulgaris) is often an abundant associate, giving rise to a distinct 
facies. In the late summer months, its delicate and purple 
panicles colour the hill sides. As lower altitudes are approached, 
this species becomes increasingly abundant at the expense of 
the mat-grass (cf. page 112). The sheep’s fescue-grass (Festuca 
ovina) is also often associated ; and this species sometimes forms 
plant societies and facies. 
The shaly hill-slopes of the Pendleside (or Yoredale) series 
which encircle the upper Edale valley afford an extensive and 
continuous expanse of Nardus pasture. On the north of this 
upland valley are the slopes of the Peak, on the south the 
slopes of the Mam Tor range, and on the east the slopes of the 
Colborne moors. Such a great expanse of Nardus grassland is 
not seen elsewhere in the district. In the sheltered Grindsbrook 
clough, the bracken (Pteris aquilina) asserts itself very strongly: 
the dwarf furze (Ulex Gallii) occurs in small patches here and 
there ; and the springs of water on the hill sides are marked by 
clumps of the common rush (Juncus effusus). 
The last three species give to the association very different 
aspects or facies. The bracken, where the soil is dry and the 
locality sheltered, sometimes occurs in extensive sheets (see 
figure 15). The gorse (Ulex Galli) is never very prominent in 
