Potamogeton.~\ 
CV. NAIADACEiE. 
481 
7. P. acutifolius Link ( sharp-leaved, P.) ; stem compressed, 
leaves linear acuminate with 3 principal and numerous close 
parallel intermediate nerves occupying the whole surface, 
spikes oval compact about equal in length to the short peduncle. 
E. B. S. t. 2609. 
Rare? Marsh-ditches at Amberley, Henfield, and Lewes, Sussex; 
Norfolk; Hertfordshire. If. 7. — The numerous closely placed 
parallel nerves well distinguish this and the following species from 
their congeners. 
8. P. zostercefolius Schum. ( Grass-wrack-like P.) ; stems 
compressed, leaves broadly linear acute with 3 principal and 
numerous close parallel intermediate nerves occupying the 
whole surface, spikes cylindrical upon long peduncles. E. B. 
S. t. 2685. P. cuspidatus Schrad. 
Rare ? Rivulet at Hovingham, Yorkshire ; River Sow, at Staf- 
ford. Lakes of Rescohie and Forfar. If. 7. — Larger than the last, 
with peduncles 2 — 4 inches long, and spikes cylindrical, sometimes an 
inch in length. Mr. H. C. Watson states that he has specimens from 
various other counties in England, but he gives no stations; it seems 
to be a species very local in each district. 
**** Leaves alternate, ovate , lanceolate,- or oblong, all pellucid and sub- 
merged ; stipules free. 
9. P. crispus L. ( curly P.) ; stem compressed, leaves lanceo- 
late waved and serrate 3-nerved sessile, fruit-beaked. E. B. t. 
1012. 
Ditches and rivers, frequent. If.. 6, 7. — Peduncles elongated, not 
thickened upwards. 
10. P. perfolidtus L. {perfoliate P.) ; stem terete, leaves 
cordate-ovate sessile and amplexicaul 7-nerved with smaller in- 
termediate nerves. E. B. t. 168. 
Ditches and lakes, frequent. Tf. 7. — Peduncles rather short, 
thick, not swollen upwards. Spikes oblong-ovate. 
11. P. preelungus Wulf. {long-stalked P.); leaves entire 
narrow-oblong semiamplexicaul obtuse and cymbiform at the 
end, with 3 principal and several lesser parallel nerves arising 
from the base connected by reticulations, stipules not winged, 
peduncles elongated, scarcely thickened upwards, spikes cylin- 
drical many-flowered. E. B. S. t. 2858. 
Lakes and pools. Ditch by Caversham bridge, near Reading; 
River Sow, at Stafford ; Rydal Water, Westmoreland ; Malham, 
Yorkshire, and several other of the eastern counties of England ; 
Berwickshire; Moss of Litie, Nairnshire; Lochleven, Kinross-shire. 
If. 7. — This is best distinguished by its oblong leaves, nerved from 
the base, where they are semiamplexicaul, and by the lengthened 
peduncle, which is sometimes slightly thickened upwards. In size it 
T 
