i 39 
The White Moss Loch. 
9 
extent. The habitat is the same in both cases and it is difficult to 
say what factor has determined the distribution. The distribution 
is therefore interesting, for it shows the same habitat dominated in 
one place by a single species and in another place by a different 
species. Divisions of an association dominated by different species 
have been described by Gleason 1 and Gates 3 under the term consocies. 
Gleason, in the part of his paper which deals with prairie formation, 
recognises four consocies in the bunch-grass association. In the 
area investigated by Gates two consocies of the bunch-grass 
association are described. While the secondary species remain the 
same, the dominant species in each of these smaller units ( consocies) 
of the association are different, although there is no obvious 
difference in their environments. This is a new use of the term 
consocies. It was originally used by Clements 3 as synonymous 
with association, but in its new sense it is particularly useful and 
descriptive. The term may be applied to describe the two areas 
into which the reed-swamp association is divided, and since 
Phragmites and Carex are the alternative dominants, the divisions 
may be designated (a) Phragmites communis consocies, ( b) Carex 
ampullacea consocies. 
(a) Phragmites communis consocies. Throughout this zone 
the common reed is dominant in some places quite to the tree line. 
At two places on the inner margin of the swamp small societies of 
Glyceria aquatica Wahlb. occur. Eastwards the zone becomes 
narrower and the Chara already mentioned in describing the 
shallow water association forms a dense growth on the sandy 
bottom. Nearer the shore where the water is still shallower the 
ground vegetation consists of Litorella lacustris L. 
At a few places just within the tree line plants of lower growth 
than the reed are becoming more abundant, indicating the 
beginnings of a marsh community. The chief invading plant is 
Comarum palustre L. and probably time will bring about the 
dominance of such humbler plants while the teeds will continue to 
advance inwards. This is already shown by the occurrence of two 
reed islands which have established themselves in the open water 
(Map, Fig. 1). There is a distinct tendency, however, for the reed 
to persist long after the surface of the soil is raised above the water 
> H. A. Gleason. “The Vegetation of the Inland Sand Deposits of 
Illinois.” Bull. Illinois State Lab. Nat. Hist., Vol. 9, 1910, p. 23. 
3 F. C. Gates. “The Vegetation of the Beach Area in N.E. Illinois and 
S.E. Wisconsin.” Ibid., Vol. 9, 1912, p. 255. 
3 F. E. Clements. “ Research Methods in Ecology.” Lincoln, Neb., 
U.S.A, 1905. Mr. Tansley informs me that Professor Clements now proposes 
to use the term in the newer sense indicated above. 
