Fallopia dumetorum (L.) Holub forma aptera (Saelán)
(Finland, Vihti, Veikkola, 1995).
– Image: Harri Harmaja (scanned from
dried specimen).
– This taxon differs
from typical F. dumetorum (Polygonaceae) through (i) the shorter
pedicels (distinctly shorter than fruit), (ii) the (outer) perianth
segments (indistinctly papillose) which are unwinged or only beset with a narrow
wing, (iii) the perianth base is short-decurrent along the pedicel (vs. long-decurrent
), (iv)
the longer nut (4 mm vs. 3 mm), and (v) a different kind of subtle
sculpture of the nut surface as seen under the dissecting microscope.
The stem is slightly angular, with very small papillae, and winds clockwise. The
lengths of the pedicel and the nut are
thus as in the closely related
F. convolvulus; however, the nut surface is almost smooth and shining as in
F. dumetorum (it is distinctly sculptured and rather mat in F. convolvulus).
Some stands
of this deviating morph of F. dumetorum occurred, obviously as
indigenous, in mesotrophic rocky hill, both
in more open shelves and in an almost vertical, mossy, slightly moist wall.
A morph of Agrostis vinealis, typical
of this microhabitat, was also present in the latter place.
F. dumetorum f. aptera has been reported from a few Finnish localities.
The taxon is thus partly intermediate between typical F.
dumetorum and F. convolvulus. However, the
nuts are well-developed so it hardly concerns a hybrid between them (which
apparently has been noted in Central Europe on very rare occasions). Neither
are the plants deformed by the smut fungus Ustilago anomala J.Kunze which
sometimes attacks F. dumetorum. As a conclusion, the present taxon may
actually be worth of the specific rank. Another apparently indigenous morph that
is closely
related to F. dumetorum, is described in my web pages as
Fallopia sp. 2.
Created August 29, 2004.