Reaction and Succession in Relation to the Plant Covering . 421 
ranges from 12-64 to 21-69 per cent. There is evidently then a tendency 
for the organic content to increase with the lapse of time. 
Summary. 
An account is given of the soils of Blakeney Point as they affect 
the vegetation, based on the examination of a large number of samples 
from phases of very diverse age, of which, however, the sequence is known 
with a high degree of certainty. 
These show that the dune systems as they grow older exhibit a 
diminution of carbonates and an increase of the organic content. Accom- 
panying these changes, which are the result of leaching and the aug- 
mented plant covering, there is a change from an appreciably alkaline 
condition exhibited by the embryo dunes to a marked acidity in the 
oldest phases. With these edaphic changes are correlated the accompany- 
ing succession in the vegetation. 
The part played by rabbit droppings in influencing the organic 
content and the reaction is considered, and quantitative data are furnished. 
The hydrogen-ion concentration is shown to vary, not only with the 
degree of leaching and organic content, but also according to the source of 
origin of the organic material and the phase of its decomposition. 
The relation between the organic content and the water-content of 
dune soils is shown to be a close one. 
The shingle banks are found to show a similar sequence alike in respect 
to reaction, organic content, and water-content, as also in stability. This is 
brought out by a study of shingle laterals of successive age, of which also 
tabulated floristic lists are given. 
The salt-marsh phases likewise show indications of increasing organic 
content, but here the important edaphic factor would appear to be the 
duration and frequency of tidal inundation. 
APPENDIX. 
Table I. Dime Soils . 
Sample No. 
Young Dunes J. and G. Series. 
p.H. 
Loss on 
i 6 nition. 
% 
Total 
carbonates. 
% 
J.030 
Embryo Psamma dune E. of Lifeboat House 
7.2 
o-37 
✓0 
°-34, 
J-°3i 
W 
» » vv * 
7-3 
o-35 
o-39 
J. 022 
>> » >) jj jj 
7-i 
— 
— 
J-023 
V }> 5J )} }} 
7-i 
— 
— 
J.024 
Rather larger than 022-023 same system 
7.0 
— 
— 
J- 032 
Very young Psamma dune on New Spit 
7-4 
0-16 
0.44 
J-°33 
,, Triticum „ „ 
7-3 
o-43 
0.46 
J- 036 
j> >} >) 
„ dune on sea-face 
7-4 
0.34 
0.32 
G. 01 
7-4 
0.52 
o-35 
G. 001 
?? >) >} 
7-4 
— 
o-39 
G. 014 
„ dune 4 in. high 
7.2 
— 
— 
G.013 
„ dune 12 in., high near 014 
7-i 
— 
— 
G.015 
Young dune near 013, 30 in. high (0-4) 
7.0 
0.30 
0.61 
G. 016 
Same as 015 (4-10) 
6.9 
— 
0.41 
G.025 
Very young outer dune 
7.2 
o-39 
0.36 
