POTAMOGETON heterophyllum.
Various-leaved Pond-weed.
TETRANDR1A Tetragynia.
G en. Char. Cal. none. Petals 4. Style none. Seeds 4.
Spec. Char. Leaves under water membranous, linear-
lanceolate, and sessile; floating ones coriaceous, elliptical,
on footstalks. Flower-stalks swelling.
Syn. Potamogeton heterophyllum. Schreb. Lips. 21.
Hoffm. Germ. ann. 1800. 81. JVillden. Sp. P I. v. 1.
713. Sm. FI. B rit. 1390.
P. palustre. Teesdale T r. o f L . Soc. v. 5. 43. Belli. 64.
P. gramineum. L ig h tf 123. FI. Ban. t. 222; without
the floating leaves.
W e received this Potamogeton from Mr. Teesdale and the
Rev. Mr. Hemsted several years ago, but have long been in
doubt about it. A collection of fine specimens, in various
states, sent from Shropshire by the Rev. Mr. Williams, have
enabled us better to understand it, and to refer it without any
hesitation to the heterophyllum of Schreber. That great author
never saw the flowers. With us they are produced from July
to September. The plant seems not to be uncommon in pools
and ditches throughout England, but has generally been mistaken,
before its floating leaves appear, which is often not till
late in autumn, for P. gramineum, because botanists have relied
on the name in FI. Danica. Mr. Turner found this plant at
Old Buckenham, Norfolk.
The roots are perennial, creeping in the mud. Stems branched.
Most of the leaves under water membranous, lanceolate
or linear, sessile; the rest floating, leathery in texture, on footstalks,
elliptical, entire, various in size and breadth. Stipulse
and bracteee large, concave, sheathing. Flower-stalks swelling
upwards, contracted under the spike, and often curved. The
upper leaves resemble those of P . natans, the only species at
all akin to this; but the flower-stalk, and lower leaves, sufficiently
distinguish them.