— 
ad 
FLORA OF ARROCHAR MOUNTAINS. 83 
4. Allt-Sugach, or the Succoth burn, one of the most inter- 
esting of the streams to the botanist, which rises in the great 
Corrie of Narnain, and flows down the steep face of the hill 
between the peaks of Narnain and Crois into Glen Loin, but 
entering the sea by a separate channel from that of the Glen Loin 
burn itself. 
5. Allt-a-Bhalachain, or the “Sour Milk burn,” occupying the 
gully between Ben Narnain and Ben Arthur. The source of this 
rather famous stream is an extensive swamp lying in the hollow 
between the two peaks, at an altitude of 2,100 feet, and offering 
many features of botanical interest, to which we shall have occasion 
to refer further presently. 
Besides these there are several minor streams, especially 
on the eastern side of Ben Vorlich, as at Stuckindroin and 
Ardvorlich, but these have not yet received the same amount of 
attention. 
The prevailing aspect of the vegetation throughout the greater 
part of the area is that of hill-pasture, the dominant species being 
grasses or grass-like plants. Heather-moors are nowhere extensive, 
the only considerable areas under heather being a large part of 
the Cruach, up to about 1,000 feet altitude, and a portion of the 
eastern slopes of Ben Vorlich, overlooking Loch Lomond. 
Woodland vegetation prevails on the banks of Loch Lomond, and 
on the side of the Cruach facing Glen Loin. There are also a 
few stretches of woodland in Glen Loin itself, one or two deep 
gullies near the head of the glen being, in particular, very densely 
wooded. The dominant trees in these woods are oak and birch, 
the former prevailing at a low elevation, whilst the birch becomes 
dominant on the hill slopes above the oak. The woodland areas 
do not reach to a high altitude except on Ben Vorlich; where, in 
the gully above Stuckindroin, the slopes are wooded up to nearly 
1,500 feet. With the exception of the areas mentioned, the 
mountain sides are mostly treeless, except along the courses of 
the larger streams. 
The hill-pasture, which covers by far the largest part of the 
district, is fairly uniform in character; its specific constitution 
varying, for the most part, within very narrow limits, as one or 
another species becomes dominant according to the nature of the 
soil; the variations in the latter being due to the presence of a 
