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P O T AM O G E T O N perfoliatum.
Perfoliate Pond-weed.
4 S
Ï È T R A N D R IA Tetragyaia.
Gen. Char. Cdl. none. Pétais 4. Style none. Seeds 4.
Spec. Char. Leaves heart-fhaped, embracing the ftem.
Syn. Potamogeton perfoliatum. Linn. Sp. PI. 182.
Mud/. FI. An. 74. With. Bot. Arr. 172. Relb. Cant.
Jo. Rati Syn. 149.
E R Y common in ponds and rivers in every part of England
; nor is it, as far as we have obferved, at all peculiar 19
a clay foil, as LinnSeus feems to hint.
Every part of the plant, except the flower-ftalks, is complete»
ly immerfed in the water, fo that it is only' to be difcover-.
ed by the fpikes of flowers about July and Auguft Handing
a little above the furface, and abounding in whitifh pollen. It
fhould feem the refpiration of fuch truly aquatic vegetables
muft be as different from the refpiration of thofe which inhale
atmofpheric air, as the breathing of fifhes is from that of beafts
and birds. Accordingly we find their leaves of an extremely
different texture, pellucid like oiled paper (as Haller remarks),
very vafcular, harfh and ribbed, but often extremely brittle.
The furface of fuch plants, like that of aquatic animals, is
deftitute of hair or down of any kind.
The italks of this Pond-weed are very long, round, with
leaves crowded about the top and branches. Thefe leaves
plight rather be called ovate than heart-fhaped, at leaft in the
moft common appearance of the plant. The petals are of a
dull purple, and fo fituated that the air eafily paffes between
them to waft the pollen to the ftigma. The feeds are com-
preffed, and ihining.