72 FLORA ORCADENSIS. 
400. P. crispus (Linn.), Curly Pond-weed. Rare. 
Rousay (R. Heddle) ; in ditch draining Loch of 
Aikerness, Evie (1882). I could not find it there 
some years later. It grows in great abundance in 
Loch of Bea, Sanday, where, in 1909, G. W. Scarth 
and I gathered specimens. 
401. P. pectinatus (Linn.), Pond-weed. Local, 
but not rare. 
There are fine specimens in Loch Stenness and 
Loch Harray. Birsay and Harray (Prof. Trail). 
402. P. FILtroRMIS (Nolte), Narrow-leaved Pond- 
weed. Fairly common. 
In Loch of St. Tredwall, Papa Westray; Harray, 
near Windywalls; Loch of Harray, Loch of Tanker- 
ness, We. 
403. P. Friesir (Rupr.), Pond-weed. Rare. 
G. W. Scearth found this in one of the lochs near 
Start Lighthouse, Sanday (12th Sept. 1909). Dr 
Boswell, Mr Ar. Bennett tells me, had previously 
reported this from Orkney. 
404. P. LUCENS (Linn.), Shininy Pond-weed. Rare. 
Mucklewater, Rousay (July 1890, Dr Fortescue) ; 
Stromness (1910, Dr Grant). “Some of the leaves 
are from 10 to 11 inches long” (Dr Fortescue). 
Dr Fortescue sent specimens of most of the Oreadian 
potamogetons to Mr Arthur Bennett, F.L.8., a botan- 
ist with an unrivalled knowledge of British potamo- 
getons. The latter gave me permission to use these 
