The White Moss Loch. 
1 37 
minimum annual temperatures average 9 , 7°F. (—12’5°C.), but in 
January, 1910,—4°P. (—20°C.) was recorded. In this year (1910) 
the loch was ice-bound for six weeks, but usually the period during 
which the water is frozen does not exceed two weeks. 
The Plant Communities. 
It is evident that the vegetation of the open water does not 
belong to the same formation as the vegetation of the surrounding 
marsh. The first and last stages in the succession from open water 
to marsh cannot be included in the same formation, but since these 
stages are gradual it is difficult to decide which of the various stages 
shall be included in the one formation and which shall be included 
in the other. 1 This difficulty applies to the reed-swamp community 
more than to any other, but for reasons given by Miss Pallis 2 the 
generally accepted classification is followed and reed-swamp is 
regarded as the terminal association of the aquatic formation. The 
vegetation of the White Moss may therefore be arranged under 
two headings:— 
I. Aquatic Formation. II. Marsh Formation. 
The distribution of the plant communities and the dominant 
species forming these communities are indicated on the accompany¬ 
ing map (Fig. 1). Because of its importance as a transitional 
stage and for the sake of clearness the reed-swamp with its 
constituent species has been shown separately from the aquatic 
formation. As already pointed out, however, its status is that of 
association. A complete bathymetrical survey of the loch was not 
made, so the contour lines on the map to show depth of water 
are only approximate. 
I.—Aquatic Formation. 
Although the water is nowhere deep, the distribution of the 
true aquatics suggests their classification into associations accord¬ 
ing to depth of water. Three associations may therefore be 
distinguished. (A) Deep water association, (B) Shallow water 
association, (C) Reed-swamp association. 
(A). Deep water association. The deepest part occurs about 
the centre of the loch, but slightly nearer the north side than the 
south. The depth is here about 1 m. and Elodea canadensis 
Michx. is dominant. The plants are remarkably tall and erect and 
1 C. E. Moss. “ The Fundamental Units of Vegetation.” New Phyto- 
logist, Vol. 9, 1910, p. 37. 
s M. Pallis, in “Types of British Vegetation,” 1911, p. 223. 
