Lamarck and Sibthorp, has been considered as a variety
of R. aquatilis by most British botanists, whilst it is looked
upon as a distinct species by nearly all tinental writers. the best of the conThe
plant now under consideration is one of the greatest
ornaments of our brooks and rivers, in which its floating
stems sometimes extend even to 20 or 30 feet in length,
their more usual length being 4 or 5 feet; they are thick,
round, hollow, smooth, branched, leafy, wholly submersed,
the flowers alone rising above the surface of the water, and
producing long fibrous roots from their lower joints. Leaves,
including their long petioles, from 3 inches to a foot or more
in length, all submersed, repeatedly di- or tri-chotomous,
with setaceous, elongated, parallel, obtuse segments; the
lower ones upon long semicylindrical stalks, the upper
sometimes nearly sessile semiamplexicaul by their broad,
dilated, membranous appendages: sometimes at the extremity
of the stem “ a tripartite leaf or two, with divergent
elliptical lobes, the central one shorter and entire, lateral
ones bifid, smooth, dark green, shining above and paler
beneath,” has been observed. Flowers large, on round,
smooth, thick, solitary peduncles. Sepals concave, ovate,
obtuse, with narrow, white, membranous margins. Petals
more than twice as long as the sepals, roundish-obovate,
blunt, often slightly crenate at the end, white, with a yellow
claw; nectariferous pores broader but shorter than in R.
aquatilis. Stamens numerous. Carpels numerous, in dense
roundish heads upon deflexed stalks, obovate, transversely
owbrtiunskele sdt,y llea.terally tipped by the short, persistent, straight,
Our present subject differs from R. aquatilis (t. 101.)
by its remarkably elongated leaves, the segments of which
are always nearly parallel, and never spread in a spherical
manner,—its obovate carpels with a lateral but straight
point, and its very different habit and remarkably larger
size: from R. circinatus its leaves, carpels, and habit at
once distinguish it. The specimens from which the drawing
was made were gathered in a brook at Cherry Hinton, Cambridgeshire,
on the 12th of June 1841, at which time it was
just coming into flower. It there grows in a swift stream
in company with R. aquatilis and R. circinatus, each of the
three retaining its peculiar characters and habit in a marked
manner. But, although it is usually found inhabiting swift
streams, it sometimes occurs in stagnant water: indeed,
some of the finest and most characteristic specimens that we
have ever seen grew, in the utmost profusion, in a stagnant
ditch near Mildenhall in Suffolk. Mr. Leighton finds it
at Shrewsbury, growing upon the moist sandy margins of
the river Severn, entirely out of the water,—when it assumes
a more caespitose appearance, but still retains all the essential
characters of the species.—C. C. B.