84 Proceedings of the Eoyal Society of Edinburgh. [Sess. 



found in non-peaty lowland areas. The typical P. polygonifolius 

 is frequently met with in peaty areas, and often in mountainous 

 districts, whilst the two are sometimes seen growing together in all 

 kinds of situations. 



Potamogeton polygonifolius, Pourr. " I.," IV., Y., VI., VII. The typical 

 form is certainly less abundant in non-peaty lochs than the form 

 approaching P. natans in size and texture of leaf, etc. 



Potamogeton polygonifolius, Pourr., var. pseudo-fluitans, Syme. IV. 

 Abundant in Loch Recar and others in the same district, as well as 

 in the streams. None fertile {i.e. in September). A very distinct 

 variety with elongated, rather pellucid leaves that are beautifully 

 netted near the midrib. 



Potamogeton rufescens, Schrad. ( = P. alpinus, Balh.). V., VI., VII. 

 Sometimes abundant, but not a very common species. The variety 

 spathulifolius, Fischer, occurs in Black Loch (p. 168). 



Potamogeton heterophyllus, Schreb. " III.," V., VII. In lowland lakes, 

 but not a very common plant in these Areas. The var. terrestris, 

 Schlecht., occurs at Loch Leven. 



Potamogeton lucens, L. "I., II.," IV., V., VI., VII. Frequently 

 abundant, and variable in form. The very large forms usually 

 occur in non-peaty lochs. 



Potamogeton Zizii, Koch ( = P. angustif alius, Bercht. and PresL). IV., 

 VI., VII. Sometimes very abundant, especially in Area VII. 



Potamogeton crispus, L. " I.," V., VI., VII. Not a very common species, 

 nor often in abundance, excepting in Area VII. At White Loch, 

 Castle-Kennedy, and in other lochs near it, a beautiful form occurs, 

 having wide, bright red midribs to the leaves. The var. serratus 

 (Huds.), which has greener, flatter leaves than the type, sometimes 

 occurs. 



Potamogeton perfoliatus, L. " I., II.," IV., V., VI., VII. Frequent, and 

 sometimes abundant. 



Potamogeton pr^longus, Wulf. " I.," IV., V., VI., VII. A deep-water 

 species (6-20 feet). Rather frequent, but seldom very abundant. 



Potamogeton Friesii, Ru2Jr. V. Only in Carlingwark Loch, where it 

 is very plentiful. 



Potamogeton pusillus, L. " L, IL," IV., V., VI., VII. Frequent. The 

 narrow-leaved form — var. tenuissimus, Mert. and Koch — occurs 

 occasionally in rather deeper water than the type. 



Potamogeton obtusifolius, Merf. and Koch. IL, V., VL, VII. Some- 

 times abundant. At Barlockhart Loch a dwarf bushy form 6-8 



