158 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY, 



character of the ground flora, nor to impair the other features 

 which stamp the wood as primitive. 



What might be termed the true type of birch " Urwald " appears 

 to be characteristic, more especially of the Highland part, of this 

 area, and may be obtained in places forming the upper limit of 

 tree-growth. This has a much wider distribution than the type 

 just referred to, and in parts may have replaced some former Scots 

 pine forest. As examples of this type, the woodlands on the 

 shores of Loch Ossian and Loch Laggan may be taken. 

 These occupy considerable areas on either side of the lochs, 

 those on the northern slopes covering a larger area, and extendmg 

 to a higher altitude than the woods on the southern slopes. From 

 the shores of the lochs (1260 feet and 830 feet respectively above 

 sea-level) the woods ascend to elevations ranging to 2000 feet, 

 at which height the trees are so isolated that perhaps the term 

 "savannah" or "scrub" might be more applicable than woodland 

 to this association. For the following reasons, one may fairly 

 apply the term "Urwald" to the above class of woodland — (i) it 

 occurs so far removed from cultivation, which, in this as in other 

 districts of the area, has never extended beyond the alluvial flats 

 of the river valleys; (2) the timber is of practically no value (not 

 even for local use as firewood) ; and (3) the positions in which 

 this type of woodland occurs are so inaccessible, that the question 

 of human agency in its formation and subsequent treatment may 

 be ruled out. 



An examination of the geological formation of the district under 

 consideration, shows the underlying strata to consist mainly of 

 schistose rocks, while glacial drift and peat form an overlying 

 soil cap. In parts, where the underlying rock projects through this 

 mask to form rugged hill tops, the greater part of the vegetation 

 is seen to be sharply arrested at the borders of the "drift." These 

 woods extend up the hillsides in a more or less phalanx-like form. 

 They show an almost complete absence of undergrowth, and the 

 density of stock is even less than in the lowland birch-woods. 

 The birch in both types is very similar as regards height and 

 diameter development, but there appears to be a difference in 

 crown development and in foliage. The commoner Highland 

 birch has a distinctly pendulous and very graceful habit, and its 

 leaves are somewhat triangular, as contrasted with the other birch 

 which is not pendulous, and has rounded leaves. 



It is in the ground flora of these Highland woods that a marked 



