ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 43 



as I know pine or birch woodland does not occur on any 2000-feet summit in the 

 Highlands. In short, the distribution of pine and birch forest and sub-arctic moorland 

 is well defined, and the two associations are not now found intermixed at the same 

 elevations and under precisely the same climatic conditions. 



This alternation of forest, arctic moorland and forest, is either good evidence of a 

 change of climatic conditions, or we must agree that in past times the different types 

 of vegetation, for some unknown cause, bore altogether different relations to one another. 

 The latter view can hardly have much to recommend it, and if accepted, would negative 

 all stratigraphical evidence. 



We see, then, that whilst some types of the Eastern Grampian mosses began their 

 history under arctic conditions, other types began to form during the latter stages of 

 the upper forest period. In each type the younger strata are the same. Arctic plants 

 occur between the two zones of the upper forest in several other areas in the Highlands, 

 whilst in nearly all, the upper forest is divided into two zones, separated by some 

 depth of peat indicating wet conditions. The presence of forest at such altitudes also 

 indicates a different altitudinal range to that of the present day, but this will be 

 discussed when describing the geographical distribution of the zones. 



(b) The eastern Peat of Ra,nnoch Muir (Ordnance Survey — sheet 54). — The moor of 

 Rannoch forms an extensive undulating region lying at 900-1500 feet, bounded on the 

 west and south by mountains rising to 3000-4000 feet, on the north by a chain of hills 

 rising to over 2000 feet. The drainage from these great watersheds passes westward 

 across the moor to Loch Rannoch, and thence by the river Tummel to Central Perthshire. 



The greater part of the moor is covered with deep peat, and this is particularly the 

 case in the area south of Loch Lydoch and along the Allt Lochain Ghaineamhaich — a 

 stream draining into the western arm of Loch Lydoch. In some places the peaty 

 covering is interrupted by beautiful sets of moraines, whose steep sides are often covered 

 with thin peat formed chiefly of Calluna. Observations were confined to the eastern 

 part of the moor, to the south and west of Loch Lydoch — an area extending to about 

 six miles by three miles. 



The vegetation over the peat-covered areas is dominated by Scirpus caespitosus, with 

 stunted Calluna, Eriophorum vagmatum (generally distributed), Rhacomitrium lanu- 

 ginosum (very abundant), Sphagnum (abundant on many of the spongy bogs near stream 

 heads, particularly in the western part of the moor). The peat is now much denuded, 

 and waste appears to be more rapid than growth. This is seen by the frequent exposure 

 of the upper forest, although, where denudation has not been so active, it is buried 

 beneath 4 feet of peat. Some difficulty was experienced owing to the amount of water 

 in the peat, and many sections had to be abandoned from this cause. The general 

 depth of the mosses ranged from 8-14 feet. 



Some interest attaches to the examination of an area of this description, as owing to 

 the probability of the lower-lying or badly-drained portions being frequently flooded, 

 much less regularity might be expected in the plant strata than on rounded hills and in 



