ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 39 



in the more exposed situations ; are always larger and persist for a greater depth in 

 the peat lying in valleys which face to the south and east ; whilst on the hill slopes and 

 in valleys which run north and north-west the remains are either very small or else 

 entirely absent. 



This is in great contrast to the distribution of the lower or the upper forest beds, 

 which are often found in positions now unfavourable for tree growth, such as the bleak 

 and treeless Outer Hebrides, and at altitudes of 3000 feet in the Highlands. 



(b) The Assynt District of Sutherland. — This district is dominated on the east by 

 the massif of Breabag, Conaveall, Ben More Assynt and Glasven, which rise to an 

 average altitude of 3000 feet. An extensive region of undulating moorland lies to the 

 south and west with Suilven, Canisp, Cul Mor, and Cul Beag rising to about 2600 feet, 

 at intervals of some miles, as isolated and precipitous hills. The general elevation of 

 the moorland is from 100 feet to 700 feet, and most of it is covered with deep peat, 

 but the hills are bare and rocky. The peat is very little broken up by denudation, 

 and the moors, intersected by scores of lochs, present a smooth and flowing aspect. 



Two areas were examined : 1, peat lying on quartzite in the valley of the river 

 Loanan, to the south of Loch Assynt ; and 2, an area near Loch Urigill about nine 

 miles farther south than the first area. 



1. Peat in the Loanan Valley. — The peat lies 300 feet above O.D. between Canisp 

 on the west and the limestone cliffs of Stonechrubie on the east. The chief vegetation 

 now is Calluna, Scirpus csespitosus, Eriophorum vagiyiatum, Narthecium ossifragum. 



The peat varies in depth from 5-8 feet ; the surface is but little denuded, and closely 

 covered with vegetation. 



Many sections taken over the southern and higher part of the moss showed the 

 following strata : — 



Characteristic Plants. 



1. Scirpus csespitosus. 



2. Pinus sijlcestris. 



3. Sphagnum. 



4. Betula nana. 



5. Betula alba of large size. 



6. Moss peat. 



Accompanying Plants. 



1. Eriophorum vaginatum. 



2. Calluna vulgaris. 



3. Traces of scrub, Betula alba. 



4. Empetnim nigrum. 



5. Corylus Aoellana. 



6. Calluna vulgaris (abundant). 



Stone pavement. 



This sequence shows three points of interest. Firstly, there are no arctic plants at 

 the base of the peat. We may infer from this, either that the record of the earlier 

 post-glacial vegetation is missing, or that the moss peat represents swamp conditions 

 which prevailed at this place immediately after the retreat of the latest glaciers. The 

 abundance of Equisetum remains in the basal zone in some of the sections taken in this 

 area rather points to the latter view as being more probable. 



The second interesting feature is the presence of a bed of Betula alba (No. 5) and 

 the Pinus sylvestris (No. 2) zone. The two layers of large trees separated by about 

 1-1-| feet of peat closely correspond to the features observed in many Highland districts. 



