J. R. Matthews. 
140 
level, perhaps because its subterranean organs are still placed in a 
saturated soil 1 (see section, Fig. 2). Thus, when once established 
the reed holds its own for a long time and this seems to explain 
why marsh vegetation is less developed on the north than on the 
south and west sides of the loch. The floristic composition of the 
Phragmites consocies is as follows :— 
Phragmites communis d. Equisetum limosum l.a. 
Glyceria aquatica l.d. Carex flava o. 
Carex ampullacea a. Alisma ranunculoides o. 
Litorella lacustris a. 
(b) Carex ampullacea consocies. This forms the terminal zone 
of the aquatic formation on the south and west sides of the loch. 
It is a marked feature of the vegetation extending 350 yards(320 m.) 
in length, and consists entirely of tussocks of Carex ampullacea 
except at points near the two extremities. At these points 
Equisetum limosum becomes sub-dominant, and in addition there is 
near the eastern extremity a small patch of Sparganium ramosum. 
The plants extend into fairly deep water and at one place Potamogeton 
natans finds shelter. Landwards this community passes into the 
marsh formation and on this side of the loch the dividing line 
between swamp and marsh is remarkably distinct. No other species 
except those already mentioned occur in the Carex ampullacea 
consocies. 
II.— Marsh Formation. 
The marsh formation includes those plant communities which 
succeed the reed-swamp and terminate in the narrow belt of willow 
and alder which forms the inner tree limit. It has already been 
pointed out that the marsh forms only a narrow zone round the 
landward side of the reed-swamp to the north and east of the loch, 
but on the south and west sides marsh vegetation is of greater 
extent. The nature of the vegetation is determined by the 
saturated condition of the soil, but the water level is probably 
responsible for marked differences in the floristic composition of 
the smaller divisions of the formation. Two associations may be 
recognised — (A) Herbaceous marsh association, (B) Alder 
willow association. The former succeeds the reed-swamp; the 
latter is the present terminal association of the marsh. 
(A). Herbaceous marsh association. In the successional 
development of this community a definite process takes place, in 
which two plants, Menyanthes trifoliata L. and Comarum palustre 
' R. H. Yapp. “ Sketches of Vegetation at Home and Abroad : WicUen 
Fen.” New Phytologist, Vol. 7, 1908, p. 76. 
