180 THE FRESH-WATER LOCHS OF SCOTLAND 
Potamogeton rufescens, Schrad.^ V., VI., VIL Sometimes abundant, 
but not a common species. The variety spathulifolius, Fischer^ 
occurs in Black Loch (Area VIL). 
Potamogeton heterophyllus, Schreh.^ III., V., VIL In lowland 
lakes, but not a common lake plant, although extremely 
abundant in Loch Cran (Area HI.). 
Potamogeton lucens, L., I., II., IV., V., VL, VII. Frequently 
abundant ; the very large forms are usually in non-peaty lochs. 
Potamogeton Zizii, Koch, IV., VI. , VII. Sometimes very abundant, 
especially in Area VII. 
Potamogeton crispus, L., I., VI. , VII. Not a common species, nor 
often in abundance. At White Loch, Castle Kennedy (Area 
VI. ), and in other lochs near it, a beautiful form occurs, 
having wide, bright-red midribs to the leaves. 
Potamogeton perfoliatus, Z., I., II., IV., VL, VII. Frequent, and 
sometimes abundant. 
Potamogeton praelongus, Wulf., I., IV., V., VI. , VIL A deep- 
water species (6-20 feet). Scarce in Area I., more frequent 
in the other districts, but seldom very abundant. 
Potamogeton Friesii, Rup7\, V. Only in Carlingwark Loch. 
Potamogeton pusillus, II., IV., V., VI. , VII. Scarce in Area I., 
frequent in the other districts. The narrow-leaved form — var. 
tenuissimus, 31. Sf K. — occurs occasionally in rather deep water. 
Potamogeton obtusifolius, Mei^t. Koch, II., V., VI. , VII. Some- 
times abundant. At Barlockhart Loch a dwarf bushy form 6-8 
inches long occurred in shallow water, normal forms being abun- 
dant in the deeper water. The var. fluvialis, Lange Mo?i., 
occurs in deep water at Burntisland Reservoir, Lismore, etc. 
Potamogeton filiformis, Pers., II., VII. Frequently abundant, 
particularly so at Loch Fitty, where, in some places, the ripe 
fruits of this plant, with those of P. pusillus, washed up on 
the shore formed a considerable stratum. 
Potamogeton flabellatus, Bab., VII. Very abundant in Town 
Loch, Dunfermline. 
Potamogeton pectinatus, /v., VII. Scarce. [VL, rare. Ravenstone 
Loch, near Sorbie. — J. M'A.] It is abundant in Duddingston 
Loch, near Edinburgh. 
Mr A. Bennett kindly examined a number of difficult forms of 
Potamogeton for me. 
CYPERACE.E 
Schoenus nigricans, L., VI. About the peaty shores of lochs ; not 
common, nor often abundant. [Frequent in damp places 
along the seashore of Wigtown. — J. M'A.] 
