£be pelopbUone formation of tbe Xeft Bank 
of tbe Severn Estuary 
By J. H. Priestley, B.Sc, F.L.S. 
INTRODUCTION. 
IN presenting" this account of some very incomplete investiga- 
tions upon the vegetation of a part of the left bank of the 
Severn estuary, I am influenced by the fact that circumstances 
will probably prevent my ever carrying- the work nearer to a 
conclusion. 
The investigation was begun really as a training- for myself in 
ecological work, and with but little idea of its subsequent publica- 
tion. However, it seems to me that for several reasons even a 
premature notice of the work may be better than none at all. 
The main reason is that the vegetation, to be subsequently 
described, is a very good example of the phenomenon of zona- 
tion, and for that reason early attracted my attention, as it is by 
no means easy to find a clear example of this phenomenon to 
bring to the notice of students. Furthermore, as will be pointed 
out, this zonation can very definitely be connected with the soil 
level and other edaphic factors. 
Another factor influencing my decision to publish is that at the 
present day a very definite need of ecology is the more minute 
study of a small tract of vegetation, such as this was intended 
to be, and I hope that the result of the publication of the work 
at this stage may be to attract the attention of other local botanists 
to the subject. Perhaps this paper may justify its existence 
by leading- later to a fuller elucidation of the interesting problems 
presented on such a clear cut scale by the sharp zones of 
vegetation on the alluvial mud stretching from Portishead to 
Oldbury-on-Severn and beyond. In the work upon this vegetation 
various workers in the Botanical Department of the University 
have at times interested themselves, and I am especially indebted 
to Miss F. Maclver for her cordial co-operation both in the tedious 
task of preparation of soil for analyses, and in the more difficult, 
if more interesting, anatomical and physiological investigations 
which have accompanied the work in the field. Unfortunately, 
at the present stage, it is not possible to utilize a large amount 
of the information so obtained ; but I hope that at some later 
time it may be possible to continue and extend the anatomical 
and physiological observations, and so subsequently make more 
complete our knowledge of the structural and physiologic adapta- 
tion shown by the local flora. I should also like to express my 
thanks to Mr. J. W. White, F.L.S., for his unfailing kindness 
when I have had need, in connection with the field work, to refer 
to him for help with systematic problems. 
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