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Proceedings of the Royal Society of Edinburgh. [Sess. 
in the water of the loch. The water is fairly clear, and is not appreciably 
peaty. The bottom of the loch from the shore to a depth of about 15 feet 
consists largely of firm sand, which is, however, frequently dirty and mixed 
with mud. Where the bottom is of this nature, which is particularly the 
case along the east side, it is usually carpeted with Chara aspera, or its 
var. subinermis, and sometimes with C. vulgaris and C. fragilis, to a depth 
of 14 or 15 feet. The growth of these plants, particularly the first men- 
tioned, at depths of from 4 to 8 feet, is prodigious, but they thin out 
towards the shallower water on the one hand, and towards the deeper 
water on the other. Nitella opaca occupies considerable areas, also where 
the bottom is sandy, and at similar depths to the Chara, but it has a 
tendency to be most abundant in slightly deeper water than that at which 
the maximum growth of the Chara occurs. On the few areas where the 
bottom from near the margin to a depth of 15 feet is of mud, as, for 
example, in some places at the west side of the loch and in the bay at the 
east end of St Serf’s Island, Anacharis Alsinastrum grows with such 
extraordinary vigour that in the summer, when the plants are near the 
surface, it is very difficult to row a boat through them.* At greater 
depths than about 16 feet no living vegetation of the higher type occurs, 
and mud covers the bottom nearly everywhere. This mud, which is usually 
blackish, with a somewhat offensive odour, was in August crowded with 
worm-like larvae at many parts of the loch. Among a number of other 
plants which grow in the water, the most abundant is probably Potamogeton 
perfoliatus. The boat-keeper at the loch informed me that previous to the 
extensive development of the Anacharis this Potamogeton was extremely 
abundant, and that it had been partially exterminated by the former plant. 
Besides those already mentioned, the following plants occur at this loch : — 
Littorella lacustris, Callitriche autumnalis, Heleocharis acicularis, Tolypella 
glomerata, but very scarce ; Myriophyllum spicatum, M. alterniflorum, 
Potamogeton filiformis, P. pusillus, P. obtusifolius, P. heterophyllus, and in 
pools on the shore the var. terrestris, Schlecht ., P. prselongus, P. Zizii, P. lucens, 
* It is supposed that this plant was introduced into Loch Leven by an itinerant hawker 
of gold-fish, who, changing the water in his tanks at the loch, threw out some of the plant. This 
is quite possible, as Anacharis is commonly used for aerating the water in aquaria, and is 
sold by dealers for that purpose. In non-peaty water containing a supply of suitable plant 
food-salts the smallest scrap of this plant bearing a whorl of leaves will grow and increase 
very rapidly, whether floating or attached to the bottom. That the Anacharis has not 
become general at other non-peaty lochs of this Area is probably because (1) it propagates 
vegetatively, as only female plants occur, consequently no seed is produced for dispersal by 
birds ; (2) the form of the plant is such that it is not likely to be carried inadvertently on 
the legs or bodies of birds ; (3) the only effluent of Loch Leven flows directly into the sea 
without entering any other loch. 
