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ox A NEW HYBRID POTAMOGETON OF THE FLUITANS GROUP. 325
* Icones,' f. 88. But by also adiiiittin sncli a plant a P. I/linonisis
Morong as equal to P. jhiitans Roth, it is evident that in this instance
be takes an extremely wide view of the term " species," since P.
llUnoensis is a form which might very well pass for a variety of P.
conacens.
After having carefully compared the very beautiful and complete
specimens from the Neckar, in Dr. Tiselius' herbarium, with
a fine series of Swedish and British forms (which exactly agree with
the description of Koth and the figure of Reichenbach), I am unable
to regard them as belonging to the same species. If we are to
admit such forms as the Neckar plant and P. Illinoeiisis of Morong
to hejluitans-iorms, then we ought also to include in the same group
such plants as P. coriaceiis and the large deep-water forms of P.
poli/noni/ulius, a length which few botanists would feel disposed to go.
How far Dr. Tiselius and I agree about the true nature of
P.fiuitiina, as figured in the ' Icones,' may be seen by the following
extract fiom a recent letter, which I have his kind permission to
publish:— "In the case of P. flnitans Roth, it has sometimes
occurred to me that P. jiuitans might be P. natans x P. lucem, but
the remarkable thing about that hybrid would then be that it is
never difficult to distinguish it from its parents as are the hybrids
of nilem, of f/ram incus, Sec. In this country the plant is no longer
foimd gi'owing in but one place, /. e., Wallstanus, where I recently
found it. How did it come thither '? Possibly brought by birds ?
Certainly both vatans and Incens grow there, but no form oijiuitims
can be taken for natans or luccns. In this country jiuitans is not found
with fruit, but, as you have probably noticed, I did find it with
fruit, somewhat developed, in the Neckar, and believe I know the
plant well. In the localities where it was formerly found in this
country it has died out for the past fifty years ; I can take young
wild specimens, in every respect similar to the cultivated ones you
were so good as to send me, in abundance at Wallstanas. It is a
remarkable plant which, it seems to me, must be looked at as a
species, in the sense that, as you remark, many a plant now considered
as being a species was originally an hybrid, and that in
process of time hybrids can produce fertile plants. Our cold climate
and water may be the reason that the leaves rot away before any
fruits have time to grow. The spikes seldom i-ear themselves above
the water, because here at WallstaniLs the plant is drawn down by
running water, but that is no proof that the plant cannot produce
ripe fruit, since fertilisation can go on under water, as, for instance,
in the case of /'. uiannus, which, in this country, never rears itself
above the water, but nevertheless produces abundance of ripe
fruits" (Dr. Gustaf Tiselius in lilt. July 1 Ith, IHUU). Taking the
plant of the 'Icones ' as the type of P. jluitan.s Roth, I would place
under it the Swedish plant from Wallstanas and the British plants
gathered by Mr. W. II. J5eeby in Sussex (iScSO) and in Surrey
(I88(jj, and those gathered by myself in Huntingdonshire (1881)
and in Cambridgesliire (1885). This form is also found in many
continental localities, as far as one can jii