FLORA OF SCOTTISH LAKES 
215 
Lythrum Salicaria, Epilobium palustre, Spiraea Ulmaria, Eupatorium 
cannabiiium, Cladophora fracta floating in the water and about 
aquatic plants, and Zygnema Vaucherii on smooth rocks, etc. 
A comparison with the hsts of plants growing in the peaty lochs 
of the Ness Area will show that some of the most dominant plants 
there, e.g. Lobelia Dortmanna, Isoetes lacustris, Callitriche hamulata, 
Juncus fluitans, etc., are absent at lismore ; whilst certain species 
flourish in the lochs of the island that do not occur in the Ness Area. 
Area III 
The Lakes near Nairn differ in many respects from those of the 
two Areas already described. The lochs in the foregoing Areas 
mostly owe their existence to the action of glaciers, and are frequently 
situated in deep valleys overshadowed by hills, or in excavations upon 
the mountains themselves, rock and precipice being a characteristic 
feature of their rugged and frequently treeless shores, while considerable 
and often great depth is a marked feature. Here, however, there are 
extensive sheets of water existing in mere depressions among former 
sandhills of the sea-shore. Their shores are flat, muddy, and, but 
for the artificial forest about them, featureless. Where vegetation is 
abundant the mud is deep and evil-smelling when disturbed. In the 
two former Areas described a continuous flat and muddy shore has 
not occurred, neither has the mud often been of the stinking kind. 
True, in many of those lochs the windward shore presents a consider- 
able stretch of bog, reclaimed from the loch by the accumulations 
formed by many generations of plants or by the detrital matter from 
a stream. It is, however, nearly always a more or less liquid peaty 
matter, not often evil-smelling when disturbed. This stinking mud, 
such as is commonly found in non-peaty lakes, e.g. Duddingston Loch 
near Edinburgh, results from the rapid decomposition of animal and 
vegetable remains. The decomposition of organic matter in these non- 
peaty waters takes place with far greater rapidity than in water charged 
with humic acids. In the first stages of decay the albuminoids are 
peptonised ; then the carbohydrates become disorganised and pass in 
gaseous condition into the surrounding water. With the advance 
of putrefaction comes the formation, among other substances, of 
ammonia, carbon dioxide, and hydrogen sulphide. It is the last- 
mentioned that gives the mud of non-peaty lakes such an ofl^ensive 
odour when disturbed. In the presence of humic acids this rapid 
putrefaction does not occur. Instead, the albuminous bodies become 
humified, and disintegration takes place slowly by a kind of carbon- 
ising process. At the bottom of Loch Ness, for example, vegetable 
remains, such as leaves, twigs, etc., first become brown, then black 
