306 NAIADACEA. [Potamogeton. 
V. Along the northern shore of Castlegregory Lake and in 
the stream leading from it : Hart 1884. Still in Castlegregory 
Lake and in swamp-pools a little to the west of the lake, 
rather sparingly, 1894.—VI. In several localities in the 
Lower Lake, Killarney, as in Castlelough Bay, along the 
Cahernane shore, on both sides of the River Flesk mouth, in 
the old mine holes, &c., on Ross Island, abundant in some 
of these localities, 1888-1904: R.W.S. 
First record in 1884: Hart, Proc. R.I.A. 
Typical P. heterophyllus appears to be very local in Kerry 
and almost confined to still water. It should, however, 
occur in the upper part of the River Laune near its exit 
from the lake, as this river for nearly its whole course of 
about twelve miles is almost filled in places with P. nitens 
and other P. heterophyllus hybrid forms. 
P. graminifolius Fries. 
Districts — — — IV. — VI. VII. — — 
Native. In swift-flowing and, rarely, in still water. Very 
rare but locally abundant. Peren. June—July. 
IV. &—VI. Abundant at intervals in the River Laune 
especially in its lower portion towards Killorglin, reaching 
to well within tidal influence: R.W.S. 1889, and in 1913. 
Rather sparingly near Rough Island in the Lower Lake, 
Killarney, 1888.—VII. The River Laune locality extends 
into this District near Killorglin: R.W.S. 
First record in 1889: R.W.S., Journ. of Bot. (as “ P. Zizit 
form”’). 
This Pondweed has been a very difficult plant to deter- 
mine satisfactorily. When first gathered, such formidable 
combinations as “‘ heterophyllus x perfoliatus x Zizit”’ and 
“ heterophyllus x Zizw’’ were suggested as its possible 
origin, and as P. perfoliatus was, next to this puzzling plant, 
the most abundant Pondweed in the neighbourhood, the 
hybrid origin suggested appeared probable. Mr. Alfred 
Fryer, however, failed to see any trace of hybridity in the 
plant and after examining a large series of specimens, fresh 
and dried, both he and Dr. Tiselius were satisfied that the 
River Laune plant was not only almost identical with 
Scandinavian “ graminifolius Fries,” but that it also agreed 
with the plant from the River Boyne, long misnamed P. 
Lonchitis Tuck., and with that from Pidley Fen, Huntingdon- 
shire. Of this latter plant, Mr. Fryer has given two ex- 
cellent plates and a full description in the Journ. of Bot. 
1892, p 38, plates 317, 318. 
