1004 Proceedings of Royal Society of Edinburgh. [sess. 
trifoliata, Carex aquatilis, etc. It will be here noticed that the 
plants are growing upon the eastern shore ; this is due to the loch 
being entirely sheltered from westerly winds by adjacent high 
hills. Moreover a considerable stream passes through this loch, 
•and the effect of its detrital matter, assisted by the vegetation, is 
rapidly filling the loch. Mr Duncan Macmillan, keeper of the 
Invermoriston forest, informed me that forty years ago the only 
vegetation in this loch was that immediately about the island with 
trees, but it has gradually been encroaching over the loch, so that 
now its waters are not available for fishing from the shore. The 
reason for the vegetation encroaching in a crescent formation over 
the loch is owing to the gentle decline and even nature of the loch 
basin ; were its bottom irregular, such a crescent formation could 
not occur. 
The rocky, barren shore of the majority of these lochs is well 
illustrated by fig. 53. Occasionally Betula nana is found spreading 
over the rocks of the shore (fig. 54). This plant is very abundant 
in the district, and often of considerable size ; the largest specimens 
I have seen had stems as thick as one’s wrist ; they are always 
prostrate. The growth of Carex rostrata, etc., in the shallower 
water of many lochs of this series is illustrated by fig. 55. 
A similar feature is shown in fig. 56, the plant being Equisetum 
limosum. The dwarf birch on an island of an otherwise treeless 
district may be seen at Loch nan Eun (fig. 57) ; the birches shown 
here are mere shrubs. I suppose the reasons for the birch only 
being found on the islands of the lochs are due to the less peaty soil 
•of the islands, absence of deer, which are very destructive to trees, 
and also because the islands escape the periodic heather-burning. 
Adjoining Loch nan Eun, whose shores are almost destitute of 
plants, are several very small lochs, almost completely over- 
grown with plants, chiefly Carex rostrata ; but for the erosive 
power of the waves and the rocky shore of the large loch, these 
plants must certainly spread to it also. Fig. 58 is a photograph 
of Loch a Mhuilinn, showing Eriophorum polystachion growing in 
the water with Carex rostrata, Menyanthes trifoliata, etc. A 
small pool that has been almost converted into terra firma by 
the vegetation is shown in fig. 59 ; the existing plants are as 
follows : — Carex rostrata, C. aquatilis, Potamogeton natans, 
