154 F. E. Fritsch and Winifred M. Parker. 
of the C U facies is also found along the path in valley A at the 
point where the clearing from the central ridge reaches this path 
(cf. the map). 
Below the limit of the Calluna-Ulex vegetation the north¬ 
western, south-western and south-eastern slopes of the ridge bear a 
dense vegetation in which Calluna, Ulex minor, Erica cinerea and, 
to a lesser extent, Vaccinium Myrtillus compete for dominance 
(CUE facies). The Calluna in this region rarely exceeds a foot in 
height and is about five years old. Ulex minor, though largely pro¬ 
cumbent (cf. above, p. 151), shows rather frequent uprising branches, 
such specimens alone appearing above the level of the surrounding 
Erica and Calluna. Bracken is much commoner (and provided 
with rather taller fronds'! over the whole of this area than on the 
/ 
ridge-top, and for a stretch of about 600 feet in the middle of the 
north-western slope becomes a dominant, the green sheet formed 
by its fronds in summer being a very conspicuous feature. Specimens 
of Pinus sylvestris, Rhamnus Frangula, Betula alba, Pyrus Aucuparia, 
Pyrus Aria and Ilex Aquifolium are scattered in this low Calluna- 
zone, being generally more abundant on the lower parts of the 
slopes, especially near the lower end of valley A. Their presence 
however in no way affects the general character of the heath- 
vegetation among which they occur. The abundance of young 
plants of some of these species (especially Betula,Pinus and Rhamnus) 
at some points indicates a trend in the direction of a birch-heath. 
On the south-western slopes Erica cinerea becomes a dominant, 1 
the heath at this point in July appearing as one purple stretch, 
when seen from a distance. 
On the opposite (south-east) slope leading down to the valley 
A we have a repetition of the vegetation on the north-west slope. 
Most of this region is occupied by the CUE facies with dominance 
of Pteridium for a stretch roughly corresponding with that on the 
north-west slope. Only a small patch of the C U facies is found 
near the path on the extreme left of the map. 
A number of grasses occur on the heath ( Deschampsia fiexuosa, 
Molinia ccerulea, Triodia decumbent, Agrostis canina), but of these 
only the first two play a really important part. Deschampsia is on 
the whole most abundant on the top of the ridge and on the upper 
part of the slopes, while Molinia is found more especially in the 
valleys and along the sides of the slopes. Analyses have shown 
’ This dominance of Erica cinerea on southerly and south-westerly slopes 
is a general feature in this part of Surrey. Standing on Gibbet Hill in July 
nearly all the southern slopes visible from there appear a deep purple. 
