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Proceedings of the Royal Society of Edinburgh. [Sess. 
west from Newburgh, which it supplies with water. It is about ^ mile 
long, and half that in width. Low hills of volcanic rock, with grassy 
or cultivated sides, and occasional plantations of coniferous and deciduous 
trees, surround it, excepting at the east end, which is more open. Although 
peat occurs on the higher hills immediately to the south and west, it is 
doubtful if any appreciable quantity of peaty water gains access to the 
loch. There is not much marshy ground, although near the effluent at the 
east end, as well as at other places here and there about the shore, small 
areas of marsh occur. Excepting for the marshy areas and a rocky part on 
the south-west, the shores consist of muddy gravel, and merge imperceptibly 
into the grassy banks. The water is clear, non-peaty, and apparently of a 
steely -gray colour, probably due to the copious deposit of black mud on the 
bottom, which arises from the rapid decomposition of a very luxuriant 
aquatic flora. Many of the submersed plants were heavily coated with a 
deposit of calcium carbonate. That beautiful species of the Polyzoa, 
Plumatella repens, was very abundant on sunken twigs, etc., and many of 
the submersed plants, particularly Littorella lacustris, were overgrown to an 
extraordinary degree with Diatomacese. On the north side there is a large 
association of Polygonum amphibium (fig. 88), which is frequently mixed 
with Potamogeton natans, and a belt of the latter extends along the outside 
of the Polygonum in deeper water. A similar phenomenon also occurs upon 
the south side, as well as a large and pure association of Potamogeton 
natans, which in this loch is of typical form, and perfectly distinct from 
any variety of P. polygonifolius. Potamogeton Zizii and a large form of 
P. lucens are both very abundant, and cover large areas of the bottom to a 
depth of 10 feet. Littorella lacustris is abundant upon the shores and in 
the water to a depth of 3 feet. Heleocharis acicularis frequently forms a 
sward upon the shore, in which condition it may be mistaken for a fine- 
leaved grass ; it also grows to a depth of 3 feet. 
Besides the above mentioned, the following plants are more or less 
abundant : — Chara aspera, C. hispida and its var. rudis, Callitriche 
autumnalis, Myriophyllum alterniflorum, M. spicatum, Ranunculus circinatus, 
R. peltatus, Potamogeton obtusifolius, P. pusillus, Castalia speciosa, 
Nymphsea lutea, Apium inundatum, Glyceria fluitans, Sparganium natans, 
Equisetum limosum, Heleocharis palustris, Sparganium simplex, S. ramosum, 
Carex rostrata, C. flava, Alisma Plantago, Glyceria aquatica, Callitriche 
stagnalis, J uncus acutiflorus, J. effusus, J. bufonius, Montia f ontana, Mentha 
sativa, Gnaphalium uliginosum, Polygonum Hydropiper, P. Persicaria, 
Ranunculus Flammula, Caltha palustris, and a few of the ordinary marsh 
and rock mosses. 
