CV. NAIADACEjE. 
483 
Potamogeton.'] 
culate or entire membranous, floating ones elliptical stalked 
slightly coriaceous, stipules strongly ribbed, peduncles thickened 
upwards. E. B. t. 1285. 
Pools and ditches, in various parts of the country. y.. 6, 7. — 
Mr. Wilson finds this sometimes without floating leaves, when it seems 
intermediate between P. lanceolatus and P. rufescens. “•The stipules, 
which are not dorsally winged, are short and broad, yet with 2 stout 
principal ribs, ovate and blunt ; both they, and the leaves subtending 
the flower-stalk, are widely spreading. Leaves distantly inserted on 
the stem; upper ones considerably larger than the rest. — Distin- 
guished by these marks, and the clavate flower-stalk from P. rufescens 
and lanceolatus Wilson. Wahlenberg, Hartmann, and Fries are of 
opinion that this is the true P. gramineus of Linnaeus; but Linnaius 
adopted that name from Ray, and Itay’s P. gramineus is the species 
commonly so called in this country. 
[Between this and the next species Mr. Babington introduces 
P. sparganiifolius Laest. ? found in the river at Maum, Galway: “sub- 
merged leaves linear narrowed at both ends very long sessile entire 
apiculate with many parallel veins next the midrib, floating leaves 
subcoriaceous lanceolate long-stalked (often wanting), stipules very 
long not winged.” With this we are quite unacquainted. Aquatics 
appear to be subject to much greater variation in appearance and 
structure than is generally supposed, so that the differential characters 
assigned are often the result of locality, and what are supposed new 
intermediate species are merely intermediate forms uniting those 
formerly recognized.] 
15. P. lunceolutus Sm. ( lanceolate P.) ; submerged leaves 
lanceolate “ not apiculate ’’ tapering at the base entire mem- 
branous with about 5 — 7 nerves connected by transverse 
veins, floating leaves elliptic- lanceolate subcoriaceous many- 
nerved petiolate sometimes wanting, peduncle about as long as 
the leaves not thickened upwards, spikes elliptical. E. B. t. 
1985. 
Pools and ditches. Anglesey. Angus-shire; Kincardineshire; 
Elgin, y.. 7. — Floating leaves are always found where the current 
is slow. “ Small chain-like reticulations are distinguishable near the 
midrib on the submerged leaves, but not on the floating leaves, 
which are elegantly overspread by them:” Wilson. The portion of 
chain-like reticulations increases gradually upwards. The difficulty 
is to distinguish this plant from P. heterop/iyllus, than which, however, 
it is much smaller and more delicate in all its parts. 
1G. P. rufescens Schrad. (reddish P.) ; submerged leaves 
lanceolate attenuate at both ends “not apiculate” entire 
membranous many-nerved with connecting veins and many 
linear reticulations at the midrib, floating ones subcoriaceous 
oblong or obovate rather longer than their stalks, stipules not 
winged, peduncles not thickened upwards. P. fluitans Sm. : 
E.B. t. 1286. 
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