150 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 muddj-- 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 jjlants were heavily coated with a 

 deposit of calcium carbonate. That beautiful species of the Polj^zoa, 

 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 Diatomacea?. On the north side there is a large 

 association of Polygonum amphibium (fig. 88), which is frequently mixed 

 witli 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 variet}^ 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 maj' 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, 

 Nymphaia lutea, Apium inundatum, Glyceria fluitans, Sparganium natans, 

 Equisetum limosum, Heleocharis palustris, Sparganium simplex, S. ramosum, 

 Carex rostrata, C. flava, Alisma Plantago, Glyceria aquatica, Callitriclie 

 stagnalis, Juncus acutiflorus, J. efi'usus, J. bufonius, Montia fontana, Mentha 

 sativa, Gnaphalium uliginosum, Polj^gonum Hydropiper, P. Persicaria, 

 Ranunculus Flaramula, Caltha palustris, and a few of the ordinary marsh 

 and rock mosses. 



