POTAMOGETON FLUITANS. LONG-LEAVED
FLOATING PONDWEED.
PO TAM O G E TO N ^wjYötw; foliis superioribus natantibus subcoriaceis oblongo-ovatis in petiolum
breviter attenuatis, inferioribus longe lanceolatis sessilibus.
POTAMOGETON fluitans. Roth Germ, m l 1. p. 72. and ml. 2. p. 202. JVilld. Sp. P I vol. 1.
p.713. Smith FI. B rit. p. 1391. Engl. Bot. t. 1286. Decand. Fl. Fr. ed. 3.
vol. 3. p. 184. FI. Gall. Syn.p. 156. Pers. Syn. PL vol. 1. p. 152. FI. Dan.
t. 1450. Alton Hort. Kero. ed. 2. vol. 1. p- 279. Hook. FI. Scot. P. I. p. 57.
Rcem. et Schultz. Syst. Veget. vol. 3. p. 504.
POTAMOGETON variifolium. Thor.e Chlor. Land. p. 47. (fide Decand.)
Class a n d Or d e r . TETRANDRIA TETRAGYNIA.
[N a tu r a l Or d e r . FLUVIALES, Rich., Hook. ALISMACEÆ, Decand., Brown. NAYADES, Juss.]
G e n . Ch a r . Flores perfecti, spadice inserti, spathacei. Perianthium tetraphyllum. Antheroe quatuor, sessües,
foliolis perianthii alternantes.. Pistilla quatuor. Nuces quatuor, monospermæ, sessiles.
G e n . Ch a r . Flowers perfect, on a spadix arising from a spatha. Perianth o f four leaves. .Anthers four, sessile,
alternating with the divisions o f the perianth. Pistils four. Nuts four, one-seeded, sessile.
Caules longissimi, fluitantes, teretes, subsimplices, fo-
liosi.
Folia alterna; superiora(plerumque duo)oblongo-ovata,
coriaceo-membranacea, viridia, natantia, nervosa,
opaca, integerrima, basi in petiolum breviusculum
attenuata ; infëriora duplo triplove longiora, lan-
ceolata, undulata, obtusa, ■ integerrima, nervosa,
nervis venis lateralibus connexis, pellucida, mem-
branacea, purpureo-viridia, basi attenuata, sed
non petiolata ; infima marcescentia, fusca.
Stipulie intra-foliaceæ, ovatæ, circa caulem convolutæ,
magnæ, diaphanæ, membranaceæ.
P e d üNCULL terminales, basi bracteati, bi-quadriunciales,
apice non raro incrassati; Bracteoe stipulis si-
millimæ.
Flores numerosi, spicati ; Spica oblonga, obtusissima.
P e r ia n t h ium simplex, tetraphyllum ; foliolis (seu po-
. tius bracteis) subrotundatis, breviter petiolatis,
coriaceis, viridibus, erecto-patentibus.
Stamina quatuor; Antheræ sessiles, posticæ, bilocu-
lares, loculis longitudinaliter dehiscentibus.
P istil la quatuor, ovata, primum erecta, demum pa-
tentia ; Stigma subsessile, capitatum.
P e r ic a r p iüM e nucibus vel drupis quatuor, subovatis,
monospermis, sessilibus ; testa valde incrassata.
Sem e n valde elongatum, curvatum, album.
Stems very long, floating under water, rounded, Subsimple,
leafy.
L eaves alternate; the upper ones (generally two) between
oblong and ovate, coriaceo-membranace-
ous, green, floating, nerved, thick, entire, their
bases attenuated into a very short pe tio le ; the
lower ones twice or thrice as long, lanceolate,
waved, obtuse, entire, nerved, the nerves connected
by lateral veins, pellucid, membranaceous, o f
a reddish green coIouf, attenuated towards the
base, but not petiolated; the lowest marcescent,
brown.
St ipu l e s intra-foliaceous, ovate, convoluted round the
stem, large, diaphanous, membranaceous.
P e d u n c l e s terminal, bracteated at the base, from
two to four inches long, not unfrequently thickened
upwards; Bracteas similar to the stipules.
F lowers numerous, spiked; Spike oblong, very obtuse.
Pe r ia n t h simple, o f four divisions; the leaflets (perhaps
rather bracteas) nearly round, upon short
footstalks, coriaceous, green, erecto-patenl.
Stam en s four; Anthers sessile, inverted, two-celled,
the cells opening longitudinally.
Pistil s .four, ovate, at first erect, subsequently patent;
Stigma subsessile, capitate.
Pe r ic a r p composed o f four nearly ovate, one-seeded,
sessile nuts, or drupas; the shell very much
thickened.
S e ed much elongated, curved, white.
Fig. 1. Flower. Fig. 2. Leaflet of the perianth, with a back view of a stamen at its base. Fig. 3. Front view
of a stamen. Fig. 4. Pistils spread out. Fig. 5. Single advanced pistil or pericarp. Fig. 6. Pericarp with
its outer coat removed. Fig. 7. Pericarp cut open vertically. Fig. 8. Seed.— A ll magnified.
The genus Potamogeton is in a sad state of confusion, partly owing to the variable nature of the species composing
it; but more, it is to be feared, to the imperfect descriptions of authors, and from a propensity to making
species out of slightly marked varieties. We shall endeavour in some measure to remove these difficulties, by giving
figures of such British species as we think may be depended upon.
With regard to the present individual, it is unquestionably the P. fluitans of Smith in Engl. Bot. 1.1286; but
I am by no means so sure of its being the fluitans of Roth, the original authority for the name. This last author
describes his plant as having all the leaves petiolated, and the petioles longer and slenderer than in P. natans, its
nearest affinity. In our specimens, as in Smith’s figure, the lower leaves are sessile, though attenuated at the
base, and the upper or natant leaves are less decidedly petiolated than in P. natans. The figure in FI. Danica
is equally characteristic with that of Engl. Bot. of our plant.
Roemer and Schultz, under the Pot. obscurum of. Decandolle, have quoted the P . fluitans Sm.; yet they transcribe
Smith’s description under P . fluitans of Roth, as referable to i t ; and there is really nothing in the specific
character of P . obscurum, “ foliis omnibus submersis alternis ovato-oblongis utrinque acutis subsessilibus multi-
nerviis integris; stipulis lato-lanceolatis,” which more properly belongs to our fluitans than in the fluitans of Roth.
From P . natans it may be known by its much longer stem, more elongated and sessile leaves, the upper ones
less coriaceous, and the submersed ones almost always inclining to a rather deep purplish green, becoming dark
brown in drying.
I t is, I believe^ of frequent occurrence; abounding in the river Blythe, by Halesworth, and in several other
parts of England. In Scotland it is found by Mr. Hopkirk in the Clyde at Dalbeth, and in ditches and lakes
near Forfar by Mr. Don. It flowers in June and July; August and September according to Smith.