156 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



typically assumes a more or less irregular strip formation, which 

 is usually rather sparsely stocked. It occurs fringing both Scots 

 pine and oak " Urwald," and is in turn occasionally skirted by 

 juniper {Jimiperus communis). In virgin forests of birch and 

 Scots pine on this area, juniper may be said to form the sole 

 undergrowth, where any is present, and, in many such situations, 

 it often shows an abnormally large development in height-growth. 

 From the variety of its distribution, birch has been well termed 

 the " weed " tree of Scotland, and if allowed scope it would, 

 without doubt, cover much of the land at present included in 

 " hill pasture" and "deer forest." 



Airhouse wood, near Lauder in Berwickshire, is here described 

 as a natural birch forest. This occupies a steep slope on the 

 right bank of the river Leader, and extends along the valley for 

 about half a mile. The wood probably owes its present state of 

 preservation to the steepness of the ground, the shallowness of 

 the soil, and the fact that it has been fenced from the surround- 

 ing agricultural land. The comparatively inaccessible position 

 of the wood also accounts, to some extent, for its present state. 

 The geological formation of the district is essentially Silurian, 

 an outcrop of which is obtained at the north end of the wood, 

 but it is almost completely masked by an extensive sheet of 

 boulder clay which overlies it. The wooded area extends from the 

 river, at an elevation of about 800 feet, to a plateau whose elevation 

 is about 1000 feet. Juniper {Juniperiis comjnunis) fringes the 

 wood on its upper margin, and appears to be suffering severely 

 from an attack of Gymnosporanghmi clavarmeforfne, which 

 probably, to some extent, accounts for its poor development 

 in this and in other similar woodlands. A conspicuous feature 

 is the predominance of hazel {Corylus avellana) in the under- 

 wood ; it occurs to such an extent as to form, in some 

 places, along with juniper, a complete second canopy. In 

 general appearance the wood is dwarfed and sparsely stocked, 

 while the individual trees are gnarled, twisted and crooked, 

 rarely having their boles clean above a height of 10 feet to 12 feet. 

 The stems and branches of the trees are clothed with lichen, 

 while the large spreading crowns cast a deeper shade than the 

 density of stock would lead one to expect. . Occasionally one 

 meets with a dead bleached stem, falling to decay, devoid ot 

 branches and leaves, and bearing the bracket-like fructifications 

 of Polyporus betulinus. The variety of birch composing the 



