134 
J. R. Matthews. 
THE WHITE MOSS LOCH: 
A STUDY IN BIOTIC SUCCESSION. 
By J. R. Matthews, M.A., 
Assistant Lecturer in Botany, Birkbeck College, London. 
[With Two Figures in the Text], 
Introductory. 
JHE White Moss Loch or the White Moss, as it is locally called, 
1 is a small sheet of water situated about two miles west of 
Dunning in Strathearn, Perthshire, Mid-Scotland. In 1901, 
according to the ordnance Survey of that year, the water covered 
an area of a little over 16 acres (c. 6-5 hectares). The land 
immediately surrounding the open water, being unsuitable for 
cultivation, has been fenced off, and in area measured (in 1901) 
about 7 acres (c. 2-8 h.). A map of the area under consideration is 
shown in Fig. 1, the boundary line indicating the fence. About 
thirty years ago the land within the fence was partly planted up 
with trees and the writer is informed that the inmost line of trees, 
consisting chiefly of willows, was placed as near the water’s edge 
as possible. This inner tree limit is shown on the map by a black 
wavy line. The above information and the nature of subsequent 
events compel one to conclude that, when the trees were planted, a 
comparatively narrow space was left between the tree line and the 
water margin. But by a gradual process of centripetal encroach¬ 
ment of various plants there has arisen a fairly wide zone of marsh 
and swamp vegetation between the tree line and the present position 
of the open water. The process is still going on ; the width of the 
marshy shores continues to increase, while there is a corresponding 
diminution of the area under water, which at present does not 
exceed 10 acres (c. 4 h.). 
Although the marsh and swamp vegetation is of limited extent, 
it shows in its development a definite succession of plant com¬ 
munities, and the consequent change in the general aspect of the 
loch is exceedingly striking. The succession has been under observa¬ 
tion for several years, and the present account is an attempt to give 
some idea of the process and of the part played by the different 
plant communities that occur, 
