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SUPPOSED HYBRIDITY IN POTAMOGETON. 177
usually barren do, however, occasionally bear fruit. By the kindness
of Messrs. Bennett and Beeby, I possess fruit of " P. jlnitans'^
from four diii'erent continental localities ; these fruits seem to fall
imder two forms, one of which the accompanying foliage shows to
be the form I regard as a distinct species, the other may be fruit of
the plant of Both, but foliage is wanting to prove this. All I can
at present claim, with any degree of certainty, is that P. Jiuitans of
the Fens is a hybrid between P. natans and P. lucens. It never
occurs but in sinf/le plaiits, and in localities so far apart as to
render it extremely improbable that fragments of living plants
sufficiently large to grow can have been carried by any natural
means.
In my previous*'note on P.decipiens-''- I gave my reasons for considering
that plant a hybrid, reasons I need not here repeat ; but
will mention one fact which suggests that P. decipiens in some
forms may possess pollen which is partly, though imperfectly,
fertile. Mr. H. Bromwich tells me that the form which he sent to
the Exchange Club as " P. decipiens, v. afftne,'" seems to be as
fertile as any other Potamof/eton. It certainly does seem so up to a
certain point. The fruit-spike swells its di-upelets till about one
half grown, then they shrivel and remain dead on the spike (in our
Fen-land decipiens the drupelets usually rot quite away).
This looks like a first effort in the direction of fertile pollen. I
do not think the stimulus that causes the swelling of the drupelets
to be foreign pollen from other species of Potatnoi/eton, because the
spikes seem to swell regularly, not a single drupelet here and there.
Mr. Bromwich informs me the plant grows apart from other forms.
That certain plants of Potamofjeton which are not hybrids may
remain barren for many years, even under apparently favourable
conditions, is a fact I have already ascertained. And I think it
is fairly well known that such supposed hybrids as P. lancenlatus
of Smitli, and P. varicms of Morong, do rarely become fertile under
favourable conditions. Hence I am not unhopeful that many
of our hybrid Potamogetons may ultimately progress to more or less
perfect fertility. To keep this note within reasonable limits I can
mention only one other instance of supposed hybridity between distinct
species of Potamofjeton. In the summer of 1889, my nephew,
Mr. C. E. Billups, sent me a remarkable form from the Kivcr Dee,
above Chester, under the name of " P. crispus.'" I at once referred
this plant to P. j)erfoUatiis, a decision which received support from
other botanists ; but Mr. Billups, a very acute naturalist, was
unable to concur, and pointed out that the stem was compressed
like that of P. crispus, and that in habit the plant resembled
that species rather than perj'oliatus. 1 planted several roots, and as
the plant gi-ew it produced young shoots from tlie axils of the
leaves on the main stem, so like those of 1'. crispus as to require
_
* My friend Mr. Beeby, wlio has often been helpful to me in my studies in
this genus, sends me the following,' correction on that note. " I do not find
' empty ' anthers on your Fen-plant. As in nitem, they are simply unopened ;
and, as in that plant, they contain plenty of pollen—of a sort."—W. 11. 13. in litt..
May 10th, 1890.
Journal of Botany.— Vol. 28. [June, 1890.] n