226 
THE FRESH-WATER LOCHS OF SCOTLAND 
carpeting species, Littorella lacustris, Lobelia Dortmanna, and Isoetes 
lacustris being the most abundant. All these plants are here over- 
grown to a great extent with Algae (p. 191). These plants, however, 
bear no external evidence of injury by the Algae ; but Nardia 
emarginata and Scapania undulata, both of which grow abundantly 
on submerged rocks, were much injured by the dense growth of such 
epiphytes upon them. In some parts, particularly at the south end. 
Sphagnum subsecundum and Heterocladium heteropterum (p. 188), 
mixed with Scapania undulata, were very abundant at the bottom 
from 2 to 8 feet deep — an uncommon situation for such plants. 
They may have been brought into the loch by one of the burns in 
time of spate, and then become adapted to the submerged environ- 
ment. I could obtain no evidence of the existence of living plants 
in this loch beyond a depth of about 10 feet, not because of the 
presence of vegetable detritus nor of the opacity of the water, but 
because in deeper, and often in shallower water too, the bottom is 
very rocky. I have noticed in many lochs that a rocky bottom is 
nearly always destitute of the higher plants, that is, when the bottom 
could be seen or felt with a pole having teeth at the end, or with 
a heavy hook attached to a line. By bumping such instruments over 
the bottom of a loch, the vibrations carried to one's hand up the 
wood or cord give an indication of the constitution of the bottom — 
mud, sand, gravel, rock, etc. Dredging over a rocky bottom is, of 
course, impossible, leaving out of the question the certainty of losing 
the apparatus. 
Loch Fleet is a somewhat oval sheet of water, surrounded by tree- 
less hills, and situated about a mile east of Loch Grennoch. It is 
about a third of a mile long, and is 1113 feet above sea-level. The 
margin is rocky, and there is very little shore suitable for the develop- 
ment of littoral phanerogams. The water is clear, and but slightly 
peaty. The flora is scanty, and is restricted to the common types 
found at Loch Grennoch. 
Loch Skerrow is situated amongst wild, rocky moorland scenery, 
four miles east of Loch Grennoch, at an elevation of 414 feet above 
sea-level. It is a shallow loch, with a very rocky shore, and with 
clear, slightly peaty water. Its bottom is covered with rocks, which 
frequently rise above the surface of the water. The larger of these 
island-rocks are often capped with vegetation of the moorland type, 
such as Calluna vulgaris, Vaccinium Myrtillus, etc. More numerous 
are the rocks which rise to just below the surface of the water. These 
necessitate caution in navigating a boat, and obviously such a rocky 
bed greatly hinders dredging operations. Sandy portions of the 
bottom, down to 12 feet deep, bore an abundant vegetation, but of 
limited variety ; otherwise there was little to be noted excepting at 
