152 F. E. Frit sell and Winifred M. Parker. 
the valley-slopes, although even on the top of the ridge occasional 
specimens with upright branches occur, these branches however 
never arising above the Calluna- level. It must be realised therefore 
that over the greater part of the Hindhead heath the Ulex minor 
is hidden from view by the growth of other constituents of the 
vegetation and is only visible at close range. At many points the 
branches of the procumbent form give rise to compact cushions, 
almost completely hiding the underlying soil by their dense 
branching. Such cushions are beautifully seen on areas recently 
burnt (PI. V, fig. 4) and on the exposed gravel slopes on the north¬ 
eastern side of the central ridge (cf. below, p. 162). 
The following forms of Ulex minor 1 can thus be distinguished 
on the Hindhead heath:—(a) the normal procumbent form, prevalent 
among the tall Calluna found on the top of the central ridge and 
at some other points, and very common on the valley-slopes; 
(b) an upright form, generally without procumbent branches, and 
found only in the valleys; (c) an intermediate form, showing both 
procumbent and upright branches, frequently found on the valley- 
slopes and more rarely on the top of the central ridge. 
There appears to be a marked tendency towards the production 
of upright shoots in Ulex minor, but it does not seem except in the 
valleys and on the lower parts of the valley-slopes that they can 
long withstand the conditions to which they are subjected. The 
most acute of these will be the drying influence of the prevailing 
winds. Many of the upright branches, especially on the upper parts 
of the slopes, show more or less advanced stages of drying up, and it 
would seem as though in these positions only those upright branches 
ultimately survive as are well protected from the prevailing winds 
by dense growth of the surrounding heath-plants. Many of the 
“ intermediate forms ” (c above) will thus by dying away of their 
upright shoots ultimately come to be of the normal procumbent 
type. When the present investigations have been carried on a few 
years longer the problem of the different growth-forms of Ulex minor 
will be definitely solved. 3 
We may next proceed to consider the constitution of the heath- 
association on the area concerned. The top and the upper slopes 
of the ridge are occupied by a growth of very tall Calluna (2£-3^ 
feet high and 10-14 years old). Standing on the flat top of the 
ridge one sees a monotonous expanse of ling, interrupted by an 
1 On some of the other heaths in this part of Surrey the upright form of 
Ulex minor is much rarer. 
1 About fifty marked plants of Ulex minor are under observation, 
