520 
VEGETATION OF BLAKENEY POINT. 
Colonisation and Succession. 
From an examination of the various phases of shingle bank 
succession there seems little doubt that the primary colonisers 
are usually forms with extensive root systems, such as Aren aria 
peploides and Silene maritima, followed on closely by Riunex 
trigranulatus. The main bank must doubtless be viewed as 
exhibiting an early condition in pebble beach colonisation, 
which condition is rendered permanent by its mobility. On the 
intermediate “ Yankee ” bank (p. 518) we still find most of the 
plants of the main bank, but with the addition of species of 
more stable situations. 
On the older laterals of the Marams the open association has 
given place to an almost continuous turf, in which the early 
colonisers are less and less abundant ; thus in the Marams 
series we find Silene maritima with less and less frequency, 
Arenaria peploides is only on banks Nos. 6 and 8, and Rumex 
trigranulatus, although present on all but three, is rare in every 
case, but most frequent on the first and second. Some of the 
annual species, such as Senecio vulgaris, Sonchus oleraceus, 
and Myosotis collina, which were frequent on the main bank, 
have been entirely driven out. 
In marked contrast is the increase of those plants which 
prefer a stable habitat, such as Sedum, Armeria, Agrostis, 
Lepturus, and Triticum junceum. Besides which there is a 
steady influx of gravel heath plants. On the “Yankee” bank 
these last are represented by a few species only, and these in 
no great abundance ; they comprise Air a prcecox, Filago 
minima, Lotus corniculatus , Plantago Coronopus, and Rumex 
acetosella, the last being the most common. Such become 
much more numerous both in species and in individuals on the 
high elbows of the older laterals. 
Factors Determining Distribution : Case of Statice 
binervosa. 
There seem then to be two factors of prime importance 
which together determine plant distribution on the shingle ; 
these are stability and the amount of accumulated soil, the latter 
in part depending on the former. The importance of stability 
