264 H. Hamshaw Thomas. 
through and quickly percolates away into the underlying limestone 
rock, but where the peat is very deep this process would be very 
slow. Owing to the impermeability of peat there would be little 
lateral movement of water, and thus the water table might well be 
at a much higher level where the peat was deep than at a point a 
few yards away where the peat was shallow. This explanation 
would be supported by the character of the flora, for while the deep 
peat on one side of the lake bears fen-carr 1 vegetation the shallow 
peat on the other side of the lake is characterised by a flora of the 
limestone bog type. 
The vegetation of the spongy bog presented an aspect almost 
identical with that of many of the East Anglian fens. The surface 
was covered in the wetter parts by a raft-like mat of Cladium 
rhizomes, with mosses, Carices and some Phragmites. The following 
plants also were abundant:— 
Peucedauum palustre. Pedicularis palustris. 
Comarum palustre. Orchis incarnata. 
Menyanthes trifoliata. Lathyrus palustris. 
In many places the last remnants of pools occurred, some of 
which contained small leaves of a Nyuiphcea, while others were 
patches of mud with Eriophorum vaginatum, Equisetum palustre 
and Drosera longifolia. As one walked over this the whole surface 
quaked and often sank below water. The underlying water was 
tested with red-litmus paper, and gave a blue coloration, but only 
after several minutes. Where the surface was a little more solid, 
bushes of Myrica Gale are plentiful, with Lysimachia, Galium 
uligiuosum, Cirsium palustre, etc. Spircea Ulmaria occurs plentifully, 
but is confined to the drier spots. These remnants of bog were 
more or less surrounded by carr consisting of a dense mass of 
shrubs about 8-12 feet high (cf. PI. V, fig. 2). The shrubs were 
chiefly birch ( Betula verrucosa ), willow (Salix cinerea and pentandra) 
and some Rhamnns Frangula. The birch is less abundant in the 
wetter places, but Alnus is comparatively rare. It may be noted 
that the marsh fern Lastrcea Thelypteris, among many other 
marsh plants, occurs in some of these carrs. It would seem as if 
we had here a series of stages in the succession of vegetation from 
the open water of the lake to the birch thicket. Both the dominant 
plants, the associated species and the apparent succession are 
very similar to those seen in our East Anglian fens. The 
occurrence of these plants is doubtless largely determined by the 
1 See M. Pallis In Types of British Vegetation, Chap. X, p. 236. 
