168 Proceedings of the Koyal Society of Edinburgh. [Sess. 



fairly common, whilst P. ruf escens, var. spathulifolius,* is extremely abundant 

 outside the zone of Nymphaea intermedia in 7 or 8 feet of water. Mr A. 

 Bennett informs me that as regards Scotland he had previously only seen 

 this variety of Potamogeton from Loch Fada, Isle of Colonsay, Argyllshire. 

 Littorella lacustris, Carex Goodenovii, Juncus eifusus, J. acutiflorus, and J. 

 lamprocarpus were the other abundant plants, whilst some other common 

 species were less plentiful. 



On the 18th of May no new shoots of Phragmites communis had 

 appeared above the water at this loch, which is about 900 feet above sea 

 level ; whilst on the previous day at Loch Gelly, which is about 400 feet 

 above sea level and only 8 miles away, the young shoots of the same species 

 were over a foot above the water. At Loch Gelly the plant grows to a 

 height of 8 or even 10 feet, whilst the form at Black Loch attains only half 

 that size. Possibly they are two distinct physiological forms, whose 

 morphological difference is most easily expressed in terms of size. It would 

 be interesting to transpose specimens from one loch to the other in order to 

 discover whether the form would change. 



Loch Dow is a small oval sheet of water situated in a hollow of 

 the grassy moor, J mile north-east of Loch Glow. The water is slightly 

 peaty, and the stony or rocky shores on the north and east are narrow, with 

 a sparse vegetation, or the moor meets the water without the intervention 

 of a shore. Extending around the south and west sides there is an 

 extensive bog, mostly occupied by Carex rostrata, which advances into the 

 water on the one hand, and merges into the grass formation of the 

 moor on the other (fig. 108). There are associations of Equisetum 

 limosum on the south and west. Hydrocotyle vulgaris is abundant 

 everywhere, and there are also a number of other common species. 



Loch Larg is a few hundreds of yards north of the last mentioned, and 

 is very similar to it, excepting that its eastern shore is more stony. There 

 is a flat boggy area along the west side, which is covered near the water 

 with Carex rostrata. Adjoining the moor this bog is overgrown with 

 Calluna vulgaris, Polytrichum commune, P. gracile, Sphagnum cymbifolium, 

 S. intermedium, etc. A slight but sudden rise of the ground causes an 

 abrupt termination to the vegetation just mentioned, and in its place 

 associations of grass-like plants, amongst which Scirpus caespitosus is 

 dominant, extend towards the moor (fig. 109). The line of demarcation 

 between the Calluna and the grass-like associations is quite sharp, and 

 probably marks the original extent of the loch. 



* Fischer, " Die Bayrisdien Potamogetonen unci Zannichellien," L'e?-. pMijr. Bot. Ges., xi. 

 (1907), pp. 20-162. 



