ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 705 
According to the geological evidence, after the warm period following the formation 
of mountain valley glaciers there was again a partial return to cold conditions, evidenced 
by the corrie moraines of the Highlands ; but this moderate degree of refrigeration might 
- eause but little change in the vegetation of the valleys in the Southern Uplands. Be 
that as it may, the pine forest in this district vanished, and its place was taken by a 
much wetter type of moorland vegetation, as the 7 feet of peat above the pine zone to 
the present surface is chiefly formed from such plants as Sphagnum, Scirpus cxspitosus, 
L., and Carices. 
As I have read the evidence, these mosses began to form some time during the inter- 
glacial period between the district glaciers and the return of glacial conditions marked 
by the mountain valley glaciers ; and if that is so, these mosses reproduce the general 
aspect of the vegétation at each succeeding period down to our own. 
At the present time the peat is not growing to any appreciable extent, and it is 
difficult to say how much peat has actually been denuded away since the cessation of 
growth. It is interesting to note that the present vegetation is chiefly made up of the 
following plants: Calluna vulgaris, Salisb.; Molinia cerulea, Moench.; Myrica Gale, L.; 
Juncus Squarrosus, L.; Erica Tetralix, L.; and a small quantity of Eriophorum 
vaginatum, L., and Scirpus cespitosus, L.; but immediately below the surface of the 
peat the remains of Sphagnum and Scirpus become dominant—evidence of the prevalence 
of an altogether wetter type of vegetation. The question of the denudation of the peat 
will be dealt with later. 
The Southern Area of the Merrick-Kells Mosses. 
A series of borings were made through the peat lying immediately south of the area 
just described. The average depth of the peat is about 15 feet. The floor of the moss 
is formed of coarse sand, through which borings were carried for 18 inches; but no 
change in the character of the sand was observed at this depth. The basal peat 
immediately resting upon the sand shows no recognisable plant remains, but consists of 
a fairly dry compact mass. Small blocks have been embedded in parattn wax, from 
which microtome sections have been made, which on examination with the microscope 
showed no structures which could be identified with certainty. Traces of vascular 
tissue in the shape of a few spiral vessels were found in one place, and pollen grains 
resembling those of the alder, and fragments of birch twigs, but nothing that would 
help to determine the conditions under which this layer was formed. Lither this basal 
peat is disintegrated drifted material from the higher peat of the north, or the earliest 
plant remains have been completely disorganised. A considerable quantity of coarse 
grit occurring amongst this basal layer suggests that the peat is really drift. 
As far as the borings show, the whole of the upper peat is formed from Sphagnum, 
Scirpus sp., and Carices, with here and there traces of Eriophorum. More satisfactory 
evidence of the history of this area might be obtained by cutting sections; but the 
