12 PELOPHILOUS FORMATION OF LEFT BANK OF SEVERN ESTUARY. 
Cochlearia was very seldom found except in sheltered positions, 
and Atriplex never occurred in exposed places, while it was found 
in profusion below New Passage w r here part of the mud zone 
was protected by a bank of shingle on the seaward side. 
Aster Tripolium L. and Triglochin maritimum L. are examples 
of plants which, while growing- freely both in exposed and 
sheltered places, showed great differences in development, averaging 
from three to six inches in height in exposed zones, as compared 
with one to two feet or more on sheltered banks. 
While Salicornia europcea L. grows nearest to the tide in ex- 
posed zones, Aster Tripolium L. is usually found in this position 
on the banks of sheltered inlets. 
The average yearly rainfall in this region is about thirty inches, 
and may be taken as fairly uniform over the whole area. As the 
rainwater is probably an important factor in removing the salt 
from the upper zones of the halophyte formation, records have 
been kept at Bristol during the whole period of investigation. 
It was impossible to make measurements on the spot, and as a 
qualitative indication of the heaviness of the rainfall at certain 
periods was all that was necessary, a central station at Bristol 
was probably as suitable for my purpose as a station at one point 
on a long strip of coast. 
THE PELOPHILOUS FORMATION. 
Turning now to the pelophilous formation, somewhat fuller 
attention must be paid to the special factors which are responsible 
for the interesting distribution of the vegetation within this area. 
This is probably the oldest strand formation present on this 
coast, and is now somewhat rapidly disappearing, being either 
scoured out by the tide or replaced by piled shingle and sand. 
There are several reasons for concluding that this formation is 
gradually going. 
(1) Old maps, and the statements of the older inhabitants, make 
this formation — for instance in the neighbourhood of St. George's 
Wharf (between Portishead and Avonmouth) — reach much further 
out into the Channel. 
(2) This formation, though outside the dune, is valuable grazing 
land, and is therefore fenced for the retention of cattle or sheep. 
In the neighbourhood of Aust several of these fences can still be 
seen dividing up a part of the coast from which by now nearly 
all the remains of this vegetation have been removed, so that the 
high tide now washes directly the exposed foot of the cliff. 
(3) The whole appearance of the pelophilous formation tells the 
same tale, the zones are fringed by curious earth pillars undercut 
by the tide, and after high tides and storms many of these can 
