Fallopia dumetorum (L.) Holub forma aptera (Saelán)
(Finland, Vihti, Veikkola, 1995).
– Image: Harri Harmaja (scanned from
– 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
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.