PELOPHILOUS FORMATION OF LEFT BANK OF SEVERN ESTUARY. 25 
In this area no indication was seen of the process of building 
up of the zones, so that I cannot state whether the same series 
of associations is passed through in reverse order, undoubtedly 
the Festuca zone can at any time be reclaimed by preventing tidal 
subsidence and cultivating. 
The relation of this series of zones to salt content and drainage 
has been investigated, and as the result of a number of analyses 
the following conclusions are drawn — 
(1) The halophytic character of the vegetation is accounted for 
by the high chlorine content to be found in all zones after tidal 
submergence. 
(2) The greater number of species present in the higher halo- 
phytic plant association can be attributed to better drainage, 
contributing with periods of good rainfall and low tides to the 
occurrence of periods of very low salt content. 
(3) The minimum salt content in the lower zones on the other 
hand is uniformly higher than the minimum content for the 
higher zones. 
(4) The reclaimed pastures owe their existence to an almost 
uniformly low saline content, to be attributed to two factors, 
(a) Infrequent tidal immersion owing to their higher level. 
(bj Improved surface drainage due to accumulation of humus. 
.REFERENCES. 
(The literature on halophyte vegetation is now very extensive, and no attempt 
has been made to compile a bibliography. I simply append a list of a 
few books and papers to which it has been necessary to draw attention 
in the text). 
Clements, F. E., "Research Methods in Ecology." 1905 edition. 
Moss, C. E., "Geographical Distribution of Vegetation in Somerset, Bath, 
and Bridgwater District," published by Royal Geographical Society, 1907. 
Smith, W. G., Botanical Survey of Scotland, III. and IV. Forfar and 
Fife." Scottish Geogr. Mag., December, 1904; January, February, ami 
March, 1905. 
Warming, E., "(Ecology of Plants," Clarendon Press, 1909. 
Wiley, H. W., "Principles and Practice of Agricultural Analysis," Vol. I., 
Soils, 1906 (second edition). 
