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NOTES ON PONDWEEDS. 139
A specimen which Dr. Tisehas has also sent me, named by him
"]'. stilivi/olius Wolf."' (and of which he says, " Hioc planta
omnino est cougruens cum speciminibus orig. a Wolfgang in fluvio
Vilia prope Wilnam lectis "), is very like the early state of a form
of r. (lecijiieiis from the Warwick Canal, kindly sent to me by ]\Ir.
H. Bromwich. This latter plant was distributed by the Exchange
Club as " P. decipiens var. affined It differs in some respects from
the type of Nolte,''' but may, I think, be placed under /*. ilecipiens.
Here also I would place a plant, distributed by the Rev. Augustin
Ley, and named " P. salicifolius Wolfg." in Lond. Catalogue, ed.
viii. I need hardly say that I am not in any way founding my
estimate of the specific states of the Herefordshire plant on Dr.
Tiselius's notes ; I formed my opinion of the position of the Here-
fordshire plant on quite independent grounds. Indeed, I have not
sufficient knowledge of the specimens and writings of the great
European botanists who have written on the genus l'ot(i)tio(/eton
to enable me to give an opinion as to whether the plants of Wolfgang
and Nolte are referable to the same specific aggregate.
Through the kindness of Professor Babington, I have been able
to examine carefully and repeatedly his unique specimen of " P.
loni/i/oliiis," and I have come to the conclusion that it is certainly a
decijiiens-form, but one that is decidedly more towards Incens than
any other I have seen. While the leaf-structure is that of decipiens,
the peduncle and flower- spike are like those of Iticens, but the flowers
Beem imperfect, and suggest that they are barren.
It may perhaps be possible for P. decipiens to be fertilised by the
pollen of other species ; but in the fens, at least, it never produces any
pollen of its own whatever, the anthers being quite empty. In spite
of this the flower-spikes are visited by insects and may rarely
become fertilised. I am not aware that any author has pretended to
describe the fruit of P. decipiens, although almost all have carefully
described the hitherto unseen fruit of P. nitens\ P. decipiens is
one of the most beautiful species known, almost equalling P. pntloiiffus
in the colour and delicacy of its leaves. In warm summers
it flowers freely, and tlie drupelets swell for a short time and give
promise of maturity which is not fulfilled. It is rather connnon
in tlie Cambridgeshire fens around Chatteris, but I have met with
one patch of it only in Huntingdonshire, just within the border of
the county at Earith.
Although we must almost certainly regard this plant as a hybrid,
I am in favour of I'etaining the specific name of Nolte, at all
events until its rank is definitely settled by actual experiment in
cross-breeding, or by more complete observation in the field. Possibly
many "species" of fertile Potamogetons are of hybrid origin; but
this note is already too long, so I must reserve any further remarks
on this subject for a subsequent paper.
• I have Mr. Bromwich's plant under cultivation, and hope tc make it the
subject of a subsequent note when more fully observed.