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138 NOTES OM PONDWEEDS.
this view is not supported by its local distribution, nor by its leafstructure
and habit of growth, which latter is that of F. perfoUatus.
This origin is also rendered highly improbable by the early flowering
of P. prtBlomjus, which is usually in fruit by
flowers of P. hicms begin to expand.
the time the first
Although mature fruit of P. decijnens is never produced, yet
isolated plants which are apparently seedlings are not unfrequently
found in remote localities, to which it is almost impossible that ofl"sets
of living plants could be carried by natural means. In
these situations a single plant only is usually found, which often
presents some slight individual peculiarity sufficient to distinguish
it alike from the type, or from other local forms. These plants are
always found growing with the supposed parents ; I have never
met with them in localities where Lucimfi and perfuliams were not
present. In waters where P. decipiens grows more abundantly it
occupies large spaces or beds, evidently by the extension of the
strong- growing rootstock ; each of these beds is composed of plants
which do not vary year after year, but it will often happen that three
or four beds, each tenanted by a slightly differing variety, occur iu the
space of a few yards, too near for local causes to produce variation,
and yet so constantly distinct as to induce the belief that each bed of
plants is the produce of a diflerent seed. Under cultivation, as far
as I have been able to observe, local forms of P. decipiens remain
very constant, which is not the case with those of some species of
FoUniKHjeton. Although these facts are not conclusive proofs of a
hybrid origin for P. decipiens, they present an accumulated weight of
evidence which is difficult to rebut.
Before I thoroughly knew this plant I frequently passed it
over in its early states as P. liicens, or when in flower as 1\ per-
foliatus. It resembles the latter species in tbe lower stipules expanded
into ear-like leaves towards the tip, and in the lower leaves,
which are nurruw and. slif/htli/ stalked in butJi species, although rarely
present in this state. The alliances, and probably the origin, of
the species of Futamorjeton must be sought in their early stages,
which often present features which entirely disappear with the
growth of the plant. Thus stipules with adnate leaves are
frequently met with on young stems of most species of Futamoffeton,
while in P. pectinatiis, belonging to a group characterised by
adnate leaves, the lower leaf is often merely sessile !
I am indebted to Dr. Tiselius, of [Stockholm, for a very
beautiful series of Swedish forms of F. decipiens, and he expresses
a very decided opinion that this species is the same as F. salicifolius
of Wolfgang, of which he possesses an original specimen
which agrees iu all respects with a form named by him 1'. uj^saliensis.
Dr. TiseHus labels a plant which is exactly like our fenland
decipiens,
" POTAMOGETON UPSALIENSIS Milli.
= salici/ulius Wolfg.
= litliiianicHs Gorski.
= lanccolatus Reich, non Sm.
Omnes fornue /'. decipientis Noltc."