The White Moss Loch. 
141 
L. play an important role. Further, the species associated with 
these two plants are different, so that two divisions of the herbaceous 
marsh association appear. These may he designated (a) Carex- 
Metty ant lies sub-association, (b) Comarum palustre sub-association t 
(a) Carex-Menyanthes sub-association. This community is 
chiefly developed on the south side and immediately succeeds the 
Carex ampullacea consocies. By the gradual deposition of plant 
remains in the Carex ampullacea community the level of the 
organic material forming the substratum is raised and when the 
depth of water does not exceed a few centimetres (five to six) 
Menyanthes trifoliata appears. When this stage is reached, Carex 
ampullacea is no longer dominant but is co-dominant with the 
Menyanthes. The community formed is quite distinct but is now 
limited to a narrow zone between the Carex ampullacea consocies 
and the Comarum sub-association. Some years ago it was much 
more extensive. At one place on the south side, however, is has 
remained unaltered for a considerable time, but here it is Carex 
filiformis which is associated with Menyanthes (see Map, Fig. 1). 
Whatever be the biological differences between this sedge and 
C. ampullacea it certainly forms a community with the bogbean 
which resists very successfully the invasion of other plants. The 
following species occur in this sub-association :— 
Carex ampullacea d, Equisetum limosum l.a. 
Menyanthes trifoliata d. Comarum palustre f. 
Carex filiformis l.d. Epilobium palustre o. 
(b) Comarum palustre sub-association. After a few years the 
accumulation of decayed vegetable matter amongst the intertwining 
rhizomes of Menyanthes forms a drier carpet of vegetation, and the 
Carex-Menyanthes community becomes invaded by Comarum palustre. 
In its initial stages this process is aided by a species of Vaucheria. 
For a year or two Comarum, Menyanthes and Carex exist together, 
but ultimately the first gains dominance and the Menyanthes entirely 
disappears. Thus the next community in the successional order— 
the Comarum palustre sub-association —is formed. Repeated obser¬ 
vations of the process have been made, and it can be distinctly 
traced at one or two places on the west side of the loch. The 
subterranean parts of Comarum become covered by a rapid growth 
of mosses, particularly Mnium punctatum, Hypnum cordifolium and 
H. cuspidatum. 1 The mosses undoubtedly do much to prepare the 
ground for other plants, for almost invariably it was among them 
1 As determined by Mr. Meldrum, 
