PELOPHILOUS FORMATION OF LEFT BANK OF SEVERN ESTUARY. 11 
It is presumably not so much a chemical action of the salt that 
is directly responsible for its effect, as a more definitely physical 
effect exerted through its presence in excess. Thus Schimper and 
others have shown that the same general type of vegetation 
characterises nitrate deposits and the sodium carbonate deposits 
of Hungary. 1 
Essentially then, a strand vegetation is to be regarded as a 
halophyte vegetation, and, perhaps, this is more particularly true 
of a mud formation lining a sea coast. The closely packed soil 
retains the salt to a far greater extent than the better draining 
soil, and probably the most characteristic halophyte vegetation 
will ultimately prove to be that of the mud, while sand and 
shingle vegetation may often fall rather into the category of the 
xerophyte. It is therefore convenient to follow Warming 2 in his 
use of such terms as lithophilous, pelophilous, &c, and in the 
limited district that I have studied, two distinct sets of problems 
are presented by the pelophilous or mud formations, and the 
psammophilous, i.e., sand or shingle formations. 
Climatic factors are the same for all the strand flora, and are 
therefore comparatively unimportant in a detailed study of a small 
area, but a very brief reference may be made to some of them 
before passing to the study of the pelophilous formation. 
Light upon the open exposed strand vegetation is obviously a 
factor that will tend to be in excess ; at the same time there is 
little indication, judging from the appearance of the plants 
during summer, when insolation effects are at their maximum, 
that this light exerts a deleterious effect upon vegetation, while 
the immediate response of the plants to a small shelter from 
the prevalent wind, even though they be still fully exposed to the 
sun, seems to suggest that the wind rather than the sun is 
responsible for the stunted growth. 
The prevalent south-westerly winds exert a very considerable 
influence upon both the appearance and the occurrence of plants 
upon the left bank of the Severn, as this bank is very fully 
exposed to winds from this quarter. The striking effect of shelter 
from the prevalent winds is one of the first factors that strikes an 
observer of this vegetation. The growth of the strand vegetation 
under sheltered conditions can readily be observed on the banks 
of the little stream just above New Passage, and on the banks of 
the Trym where it joins the Avon at Sea Mills. 
Some plants are very seldom found on the wind-swept zones 
lining the Severn bank, but appear immediately shelter is provided 
by a ditch or the angle of a small stream. The most striking 
examples of this are the species Cochlearia anglica L. and Atriplex 
has tat a L. 3 
1 Warming loc. cit. p. 218. 2 Loc. cit. p. 223. 
3 The nomenclature in this paper follows the list of British Seed Plants and 
Ferns, published by the British Museum, ]907, and revised by Bendle & 
Britten in accordance with the rules of nomenclature adopted at Vienna, 1905. 
