4io Salisbury . — The Soils of Blakeney Point : A Study of Soil 
larly, to other types of vegetation (cf. Journal of Ecology, vol. ix, pp. 320-40, 
1922), leaching being most rapid at the crest of a hill or the upper part ol 
a valley slope, the flora tends as a rule to become more calcifuge in character 
as we ascend. It is in conformity with this generalization that, as pointed 
out by W. G. Smith for the dunes of Fife, Calluna vulgaris and Erica 
cinerea occur more particularly towards the crest of the dune ridges 
(loc. cit, p. 71). 
Even in these old dunes, with their low proportion of plant food, the 
hollows support a type of vegetation which bears much the same relation 
to the calcifuge flora of the ridges as the path and valley-bottom vegetation 
bears to that of the general woodland vegetation in an acid oak wood (cf. 
Salisbury, Journal of Ecology, vols. iv and vi, ‘ The Quercus-Carpinus 
Woods of Hertfordshire ’). 
The extreme calcifuge character of ancient dunes is sufficiently 
emphasized by the fact that such species as Corallorrhiza innata , Vaccinium 
myrtillus, V. Vitis-idaea, and Pyrola rotundifolia have been recorded from 
old dune systems in this country. That other dune systems show the 
same feature as those of Blakeney is illustrated by the data given on p. 400 
for a series of samples from the Southport dunes. 
The dune soils exhibit the usual humus gradient (cf. Salisbury, Journal 
of Ecology, vol. ix, p. 221), which is well illustrated by the appended data 
from two areas on the Long Hills, one covered by vegetation and the other 
bare, as well as by the estimations already furnished. 
Depth. 
No vegetation. 
Vegetation. 
in. 
0-6 
6-12 
12-18 
3-9 6 
1-14 
o-93 
It is this increase in humus in the surface layer that is probably 
mainly responsible for the colonization of the younger ‘ fixed ’ dunes by 
Tortula ruraliformis and other mosses. Although relatively dry in 
summer the surface soil, from its comparatively high organic content (cf. 
D 36-D 48, D 43, &c.), ensures considerable moisture during the winter 
months. 
In the Blakeney system Triticum junceum, Arenaria peploides, Festuca 
arenaria, and Eryngium maritimum are more or less restricted to the 
earlier ‘ yellow ’ dune phases. In the more stabilized condition Psamma 
decreases in amount and the individuals exhibit diminished vigour. 
On the ridge D mosses, particularly T. ruraliformis, Carex arenaria, 
Erodium, &c., make their appearance. 
