148 
The White Moss Loch. 
usually when dealing with large areas. Miss Pallis’ has described 
the succession from reed-swamp to fen associations, with which the 
marsh formation has a good deal in common. At the White Moss 
the initial stages are commenced when Carex on the one side and 
Phragmites on the other establish themselves in an advancing zone 
along the water-margin. The reed-swamp is an important transi¬ 
tional stage in the succession, for the accumulation of its organic 
debris prepares the way for the development of a new formation. 
Thus the series progresses from the aquatic formation to the ultimate 
development of a mesophytic community. 
In the process the part played by Comarumpalustre is remarkable, 
for this plant succeeds equally well in its invasion of the preceding 
stage whether the soil is being formed on the one hand from the 
decayed plants of Phragmites, or on the other from the remains of 
Carex and Menyanthes. 
Conclusion. 
The “drying up” of the White Moss seems only a matter of 
time, for the centripetal encroachment of the marginal vegetation 
is fairly rapid. At one point on the south side where measurements 
have been made, the inward advance for the past ten years has been 
at the average rate of 1*3 m. per annum. But the rate of advance 
may vary from place to place. Along the eastern margin wave- 
action tends to obstruct the development of swamp vegetation, 
while its production goes on faster on the opposite side, which is 
towards the prevailing wind. Further, the slope of the substratum 
is gentlest from the west side of the loch, and this probably aids in 
the more rapid building up of the vegetation along this margin. As 
this development goes on the lake-stage will ultimately become 
extinct, and the first formation to remain stable will probably be 
marsh. But a few self-sown willow bushes have already appeared, 
and it is natural to conclude that in the course of time, an area 
will be presented completely devoid of open water but covered with 
a thicket of willow and elder. 
In conclusion, the writer wishes to express his sincere thanks 
to Mr. Tansley for bringing to his notice the American publications 
mentioned on page 139 in which the term consocies is discussed in 
its new sense, and for much valuable criticism during the preparation 
of this paper. 
1 M. Pallis. “Fen Formation of East Norfolk,’’ in “Types of British 
Vegetation,” 1911, p. 230. 
