1909-10.] Flora of Scottish Lakes. 165 



substance. At other places upon this side of the loch the shore is gravelly 

 or sanely, and bears more plants than the opposite side does. The chief 

 affluent enters the loch at the west end, previous to wliich it has a v^ery 

 sinuous course for about a mile through an alluvial flat consisting of pasture 

 or arable land, doubtless at one time covered by the water of the loch. 

 Near the loch this flat merges gradually into a bog several acres in extent 

 (flg. 104). At the east end, whence flows the effluent, and where also another 

 burn enters the loch, thei'e is a similar but much less extensive bog (fig. 10.5). 

 The loch is shallow throughout its area, a depth of 10 feet being seldom 

 exceeded. The deepest water occurs opposite the mine on the south shore, 

 where a depth of 17 feet may be sounded ; this depth is probabl}^ due to 

 the bottom sinking on account of the mining operations below. The photic 

 zone extends to a depth of 12 feet, beyond which black mud occurs and no 

 living vegetation. The stones about the shores are nearly everywhere 

 thickly covered with Cladophoras, which bear an extraordinary quantity of 

 Diatomacea3, chiefly of the genera Diatoma, Gomphonema, and Cocconeis. 

 A remarkable feature is the vast amount of Potamogeton pectinatus growing 

 in water from 6 to 12 feet deep, the slender stems carrying the flowers to 

 the surface even from the greatest depth. Here and there at the marshes 

 are pure groups of Iris Pseud-acorus, with leaves 4 or 5 feet high, standing 

 out of the water as little islands. A considerable portion of the bottom is 

 covered with Chara fragilis and its vars. fulcrata and delicatula, C. aspera 

 and its vars. subinermis and capillata, and C. contraria, as well as with a 

 number of other plants. Litorella lacustris and Heleocharis acicularis are 

 scarce. Callitriche autumnalis is very abundant ; besides the type tliere is 

 a form differing slightly in the leaves and fruit. About the marshes 

 aquatic and terrestrial forms of C. stagnalis abound. Potamogeton 

 rufescens, the type as \vell as a very leafy, barren form, is abundant. 

 P. pusillus, the type as well as a narrower-leaved form, P. fllifonais, the 

 type and a much longer-leaved form, and P. pectinatus are all very 

 plentiful; indeed, the three last-mentioned species are so abundant that 

 their fruits, which in the autumn are washed upon the shore, formed in 

 a few places a stratum over the sand an inch deep. Potamogeton 

 perfoliatus, P. Zizii, and P. obtusifolius are all very abundant, while P. 

 prselongus, P. natans, and P. polygonifolius are all scarce. Myriophyllum 

 spicatum is very plentiful, but M. alterniflorum is scarce. Anacharis 

 Alsinastrum occurs sparingly, and the plants are weak. The following 

 also occur, but none of them is abundant : — Nitella opaca, Juncus fluitaus, 

 Ranunculus peltatus, Nymphaea lutea, Polygonum amphibium, Sparganium 

 simplex, var. longissimum, the last near the affluent at the west end, and 



