Root creeping extensively in the mud. Stems cylindrical, vary- 
ing in length, often many feet, much branched, leafy. Upper 
leaves opaque, leathery, smooth, deep green or tinged with brown, 
2 or 3 inches long, elliptical, often heart-shaped at the base, with 
about 7 main ribs, and several intermediate smaller ones ; floating 
on the surface of the water like those of the water-lilies ; involute 
in the bud. Lower leaves submersed, alternate, strap-shaped, 
acute, very narrow, tapering gradually into a footstalk (petiole) ; 
these submersed leaves are frequently wholly wanting. Petioles 
(footstalks J of the floating leaves various in length, semicylindrical, 
very vascular. Stipxilas (see section at the bottom of the plate) 
intrafoliaceous, large, spear-shaped, pointed, concave, pale and 
membranous, nearly as long as the petioles. Spikes simple, raised 
an inch or two above the- water, each on a long, thick, axillary 
stalk, which is suddenly contracted at the bottom of the spike. 
Flowers a little distant, quite sessile, rather numerous, vertical, 
olive-green. Anthers yellow, with whitish pollen. 
The leaves floating upon the surface of the water afford an agree- 
able shade to fish, and are the habitation and food of Phalana 
Potamogata. The roots are sometimes eaten in the wilds of Sibe- 
ria by men, but in more temperate regions they are fed on only by 
swans, who devour them with' avidity. Mr. Stackhouse says, 
their love of this plant is such, that a pair of them, by harass- 
ing it in search of its succulent roots during winter, almost destroyed 
it in the whole extent of nearly five acres of water, which at times 
had been completely matted over with it. 
Linnaeus remarks, that when this species grows in water which 
is dried up in Summer, it surprisingly changes its appearance, be- 
coming upright, and resembling a small Plantago. In this variety 
the stem is said to be but about four inches high. The sheaths of 
the peduncles and petioles less than half the length of their re- 
spective stalks. The leaves alternate, except the upper pair ; the 
lower ones spear-shaped, on long petioles ; and the upper ones 
oval, with shorter petioles. It flowers a month or six weeks earlier 
than the common plant. 
The Natural Order , Fluviales, to which the present genus be- 
longs, consists of monocotyledonous water plants, whose leaves are 
very vascular, with parallel veins. Their flowers are inconspicuous, 
perfect or monoecious ; and usually arranged in terminal spikes. 
The perianthium is composed of 2 or 4 pieces, often deciduous, 
rarely wanting. The stamens are definite, and hypogynous. The 
ovaries 1 or more, superior ; with a simple stigma ; and a solitary, 
pendulous ovule. The fruit is dry, 1-celled, 1 -seeded, and inde- 
hiscent. The seed is pendulous ; and the embryo without albumen, 
having a contrary direction to the seed, with a lateral cleft lor the 
emission of the plumule. 
This order contains the following British Genera. 1. Polamogc- 
ton, t. 350. — 2. Zoslcra. — 3. Rvppia. — 4. Zannichcllia, t. 164. 
