168 Proceedings of the Royal Society of Edinburgh. [Sess. 
fairly common, whilst P. rufescens, var. spathulifolius,* is extremely abundant 
outside the zone of Nymphsea 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 elfusus, 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 Geliy, 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 Geliy 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, \ 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 
iimosum 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 csespitosus 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, li Die Bayrischen Potamogetonen und Zannichellien, 55 Ber. Bayr. Bot. Ges., xi. 
(1907), pp. 20-162. 
