Botanical Journal of the Linnean Sociery ( 1988), 98: 321-37!. With 31 figures
Generic limits in Polygonum and related
genera {Polygonaceae) on the basis of
floral characters
LOUIS-PHILIPPE RONSE DECRAENE* AND j. R. AKEROYD, F.L.S.
Botany Department, Plant Science Laboratories, University
Reading RG6 2AS
of Reading,
Whiteknights,
Received September /987, accepted for publication February 1988
RONSE DECRAENE, L.-P. AND AKEROYD,J. R., 1988. Generic limits in Polygon•m and
related genera (Polygonaceae) on the basis of ftoral characters. In order to investigate the
taxonomic value of a number of characters in the elucidation of relationships within the collective
genus Polygonum L., and segregate genera Atraphaxis L., Calligonum L., Pteropyrum Jaub. & Spach.,
Ox_y.~onum Burch., Fagop_yrum Mill., Harpagocarpus Hutch. & Dandy and Polygonella Michx., 83 species
of the tribe Polygoneae emend. Jaretzky were studied. The following floral characters were
examined: stamen number, insertion and external morphology; structure and morphology of the
floral nectaries; vasculature and surface morphology of the tepals.
Problems in floral morphology in Polygonaceae are discussed, together with relationships within
the family. The tribal division proposed by Haraldson ( l 978) is supported, but a new and different
delimitation of genera is proposed. The present data support a division of Polygonum L. sensu lato and
its related taxa into two tribes: Polygoneae (containing Polygonum L. sensu stricto, Fallopia Adans.,
Ox_y,~onum Burch., Pterop_yrum Jaub. & Spach., Atrapkaxis L. and Calligonum L.), and Pt>rsicarit>ac
(containing Fagopyrum Mill., Harpagocarpus Hutch. & Dandy, Persicaria Mill. and Koenigia L.). The
genus Reynoutria Houtt. is included as a section of Fallopia Adans.; Bistorta Mill., Aconogonon
Rcichenb. and Tovara Adans. are included within Persicaria Mill.
A number of new combinations art> proposed in Persicaria and Fal/opia.
ADDITIONAL KEY WORDS:-Filament morphology- nectaries- papillae- stamen insertiontaxonomy- tepa! anatomy.
CONTENTS
Introduction .
Characters investigated
Material and methods .
Results
Discussion .
The generic approach.
l. Tribe Persicarieae
Persicaria Mill.
Komigia L. emend. Hedb .
Fagopyrum Mill. .
Harpagocarpus Hutch. & Dandy
2. Tribe Polygont>ac
Polygonum L. .
322
325
328
329
330
330
330
331
338
339
340
340
340
*Present address: Laboratory of Systematics, Institute of Botany, Catholic University ofLeuven, Kardinaal
Mercierlaan 92, B-3030 Lcuven (Heverlee), Belgium.
321
0024-4074/88/120321 +51 $03.00/0
©
l 988 The Linnean Society of London
L.-P. RONSE DECRAENE AND J. R. AKEROYD
322
343
344
346
346
347
347
348
350
352
352
354
366
370
Po/ygonel/a Michx.
Fallopia Adans.
Oxygonum Burch ..
Pteropyrum jaub. & Spach.
Atraphaxis L. .
Calligonum L. .
Discussion of the characters used
Conclusions
Acknowledgements
References.
Appendix I
App~ndix 2
Appendix 3
INTRODUCTION
Polygonum L. has remained a major challenge for taxonomists since Linnaeus
( 1753) established the genus as a loose but not entirely successful unit.
Many authors have tried to subdivide the genus into more natural units at
TABLE
Meissner
(1826)
I. Summary of the most important classifications of Polygonum sensu lato at generic
and sectional level together with present proposal
Meissner
(1857)
•Bentham & Hooker
(1880)
Gross ( 1913)
Danser
(1927)
Jaretzky
(1928)
Steward
(1930)
Auicularia
P. sect. Tephi.r
Polygonum
P. sen. Avicularia
Polygonum
P. sect. Tiniaria
Tiniaria
P. sect.
Tephis
P. sect.
Avicularia
P. sect.
Tiniaria
Fagopyrum se<"l.
Tiniaria
P. sect.
Tiniaria
P. sect.
Persicaria
P. sect.
Tiniaria
P. sect.
Persicoria
P. sen. Pleuropterus
Pleuropterus
P. sect. Per.ricaria
Pt:rsicaria sert.
Euptrsicario
P. sect.
Bistorta
P. sect. Ptr.ricaria
Bistorta
P. sect. Aconogonum
Aconogonon
P. sect.
Bistorta
P. sect.
Aconogonon
P. seet.
Aconogonon
P. sect.
Amhlygonon
P. sect.
Amhlygonon
P. sect. Persicaria
Persicaria sect.
Aconogononf
Pleuroptrrop_vrum
Persicaria sect.
Amblygonon
P. sect.
Persicaria
P. sect.
Per sicaria
P. sect.
Persica ria
P. sect.
Cephalophilon
P. sect. Cephalophilon
Persicaria sect.
Cephalophilon
P. sect.
Cephalophilon
P. sect.
Cephalophilon
P. seet.
Cephalophilon
P. seet.
Echinocaulon
P. sect. Cephalophilon
Ptrsicaria sect.
Echinocaulon
P. sect.
Echinocaulon
Echinocaulon
P. sect.
Persicaria
P. sect.
PtrJicaria
P. sect. Tovara
Ptrsicaria sect.
Tovara
P. set·t.
Avicularia
P. sect.
Avicularia
Polygonella
P. sect. Pseudomollia
Polygonum
P. sect. Avicularia
Polygonum
P. sect.
Pseudopolygontlla
Polygonella
P. sect.
Avicularia
P. sect.
P. sect.
P. sect.
PtrJicaria
P. sect.
Fagopyrum
P. sect.
Cephalophilon
Fagopyrum
Fagopyrum
P. = Polygonum
•Dammer (1893) follows exactly the same treatment.
Persicaria sect.
Cephalophilon
Fagopyrum sect.
Eujagopyrum/
Pteroxygonum
P. sect.
Avicularia
P. sect.
Tiniaria
Am'cularia
P. sect.
Tiniaria
P. sect.
Persicaria
Polygonum
P. sect.
Tiniaria
P. sect.
Persicaria
P. sert.
Persicaria
P. sect.
Bistorta
P. Sel·t.
Aconogonon
Polygonum
Penicaria
P. sect.
Avicularia
P. sect.
Tiniaria
Ptrsiraria
P. sect.
Tovara
Polygontlla
Fagopyrum
P. sect.
Cephalophilon
P. sect.
Fagopyrum
GENERIC LIMITS IN POLYGONUM
323
subgeneric, sectional or generic rank. Which rank should be used is still a great
matter of debate, as the accumulated data have perhaps not been digested
sufficiently to attain a convincing conclusion. Meissner ( 1826) subdivided
Polygonum L. into seven sections: Bistorta, Aconogonon, Tiniaria, Avicularia,
Persicaria, Fagopyrum and Amblygonon (see Table 1). Later Meissner (1857)
extended these to nine ( Tephis, Avicularia, Persicaria, Amblygonon, Cephalophilon,
Echinocaulon, Bistorta, Aconogonon, Tiniaria), and separated Fagopyrum and
Polygonella as distinct genera. Bentham & Hooker ( 1880) recognized more or less
the same groups as Meissner (1857) but added a few sections (Pseudamollia,
Pseudopalygonella and Pleuropterus). Watson (1873) separated section Duravia, with
P. californicum as the only species.
The first attempt to recognize different genera in Polygonum was made by
Gross (1913a, b) who maintained some of Meissner's sections, but divided the
genus into seven genera (Pleuropterus, Pteroxygonum, Pleuropteropyrum, Polygonum
sensu stricto, Bistorta, Fagapyrum and Persicaria) on the basis of gross morphology
and pollen characters. J aretzky ( 1925) separated the genera Polygonum
Hedberg (1946)
Love & Love
(1956)
Graham &
Wood (1964)
Polygon urn
Polygonum
Po/ygonum
Polygonum
P. sect.
Tiniaria
Bi/derdykia
Polygonum
P. sect.
Tiniaria
Tiniaria
Reynoutria
P. sect.
Tutin el a/.
(1964)
Roberty &
Vautier (1964)
Hara ( 1966)
P. sect. Tephi.r
Polygonum
P. sect.
Polygon urn
Bilderdykia
P. sect. Avit'ularia
Polygon urn
Bi/dmiykia
Bi/derdykia
Reynoutria
Reynoutria
P. sect.
Persicaria
P. sect. Persicaria
Haraldson
(1978)
P. sect.
Tephi.r
P. sect.
Polygonum
Fallopia
Re_ynoutria
Tiniaria
Per.ricaria
Bi.rtorta
Persicaria
P. sect.
Persicaria
P. sect.
Tephis
P. sect.
Ar,icularia
Fallopia sect.
Sarmento.raef
s. Fallopia
Fallopia sect.
Reynoutria
Persicaria
sect.
P. sect. Bistorta
Bi.rtorta
Persican·a
Ronse
Decraene
Bi.storta
Persicaria
Bistorta
Persico ria
sect. Bistorla
Pleuropteropyrum
Persicaria
Persica ria
Per sica ria
Ptrsicaria
Pleuropteropyrum
Aconogonon
Per.ricaria
P. sect.
Persicaria
P. sect.
Cephalophilon
Persicaria
Ptrsicaria
Tovara
P. sect.
Echinocau/on
P. sect.
Echinocaulon
P. sect.
Tovara
Polygone//a
P. sect.
Echinocaulon
Aconogonon
P. sect.
Polygonum
Polygone//a
sect.
Persicaria
Ptr~icaria
sect.
sect.
Persicaria
Cephalophi/on
Per sica ria
Persicaria
Persico ria
sect.
se(·t.
Persicaria
Cephalophi/on
Persicaria
Ptrsicaria
Persicaria
sect.
sect.
Echinocaulon
Persicaria
Dura via
Polygone//a
Ptrsicaria
Persiraria
sect.
Tovara
P. sect.
Polygonum
P. sect.
Polygonum
Polygone// a
Koenigia
Koenigia
Koenigia
Fagopyrum
Fagopyrum
Fagopyrum
Persicaria
Antenoron
Tovara
P. sect.
Polygonum
P. sect.
Polygonum
Polygone// a
Fagopyrum
P. sect.
Eleutherosperma
Fagopyrumf
Pteroxygonum
PeTJicaria
Aconogonon
P. sect. Polygonum
Fagopyrum
Aconogonon
sect.
Koenigia
Fagopyrum
P. sect.
Cephalophi/on
Antenoron
Polygonum
Polygonum
P. sect.
Aconogononf
Ampelygonum
Ampelygonum
P. sect.
L.-P. RONSE DECRAENE AND J. R. AKEROYD
324
(including sections Pleuropterus and Tiniaria), Avicularia (including sections Tephis
and Avicularia), Persic aria and Fagopyrum, mainly on the presence versus absence
of antrachinones. Danser ( 1927) and Steward ( 1930) retained six and eight
sections respectively within Polygonum, but the latter also separated the genus
Tovara. Hedberg ( 1946) split Polygonum into seven genera, mainly on the basis of
pollen morphology ( Koenigia, Persicaria, Polygonum sensu stricto, Pleuropteropyrum,
Bistorta, Tiniaria and Fagopyrum). The related genus Koenigia was emended to
include species of Polygonum sensu lata. Haraldson ( 1978) proposed a similar
treatment and distinguished eight genera (Aconogonon, Koenigia, Persicaria,
Reynoutria, Bistorta, Fallopia, Polygonum, Fagopyrum) in two different tribes, mainly
on the basis of anatomical features. Roberty & Vautier ( 1964) set up an
independt>nt system with seven genera in several unrelated tribes (Polygonum
sensu stricto, Bilderdykia, Reynoutria, Ampelygonum, Fa,gopyrum, Pteroxygonum and
Antenoron) mainly based on the structure of the stigmas and propagules. The gap
between Polygonum sensu lata and other related genera of Polygonaceae
(Oxygonum, Pteropyrum, Calligonum, Koenigia, Atraphaxis and Polygonella) was
consequently narrowed, as splitting reduces the integrity of the genus. The tribal
treatment of Polygonum sensu lata has not been unanimous, and several authors
have separated different taxa into distinct tribes or subfamilies (see Tables 2 and
3). Haraldson ( 1978) proposed the division of Polygonum sensu lata into two tribes,
Polygoneae and Persicarieae. Her work on the subgeneric division of Polygonum
L. has overturned all previous schemes of relationship. She maintained eight
genera in three different tribes, exceeding the traditional limits of Polygonum sensu
lato (see Table 2).
The classification of Polygonum sensu lata has thus remained confused until the
present, although serious attempts have been made to evaluate taxonomically
important characters. The early classifications were based mostly on gross
morphological characters. The use of other characters, such as anatomy
(Perdrigeat, 1900; Laubengayer, 1937; Vautier, 1949; Haraldson, 1978), pollen
(Gross, 1913a, b; Wodehouse, 1931; Hedberg, 1946; Nowicke & Skvarla, 1977),
TABLE 2. The position of the genera studied in the Polygoneae in their respective
tribes. Refer to Table 3 for subfamiliar rank
Genera
Po[vgonum sensu stricto
Persicaria
Bistorta
Fa.gopyrum
Pteroxygonum
Aconogonum
Rrynoutria
fallopia
Bilderdykia
Antenoron
Koenigia
Po[vgonella
Atraphaxis
Calligonum
Pteropyrum
09gonum
Harpagocarpus
Meissner ( 185 7)
Bentham & Hook.
(1880)
Eupo1ygoneac
Eupo1ygoneae
Eupo1ygoneae
Eupo1ygoneae
Eupo1ygoneae
Ceratogoncac
Ccratogoneae
Calligoneae
Rhabarbareae
Rhabarbareae
Koenigicae
Eupo1ygoneac
Eupo1ygoneae
Eupo1ygoncae
Eupo1ygoneae
Eupo1ygoneae
Baillon ( 1892)
Po1ygoni-es
RumiC.:·es
Po1ygoni-es
Po1ygon(·es
Po1ygoni-es
Po1ygonces
Po1ygonees
GENERIC LIMITS IN POLYGO.NUM
325
chromosome numbers (Jaretzky, 1928; Love & Love, 1956; Mahony, 1935) and
chemical substances (Jaretzky, 1925) has provided a considerable amount of
data for those who wish to split the genus, as, taken together, they stress the
distinctness of several natural groups within it.
In this comparative treatment of the genus we have followed mainly the
generic scheme of J aretzky ( 1925) in his tribe Polygoneae as a framework; this
includes the taxa in Polygonum sensu lato, as well as the closely related genera
Koenigia, Fagopyrum, Polygonella, Atraphaxis, Pteropyrum, Calligonum and Oxygonum.
In the treatment of Polygonum sensu lato, certain characters have previously
received more attention as they are more obvious, or because they have been
traditionally considered to be more important. The inflorescence, pistil and
fruiting perianth, as well as the ochrea and other vegetative structures, have
been used extensively in major classifications. We have concentrated on some
less obvious floral characters, such as stamen insertion, tepal morphology and
anatomy, and the structure of the nectaries.
CHARACTERS INVESTIGATED
The basic floral structure of Polygonum sensu lato is a pentamerous perianth
that is built up in an acyclic manner, with eight stamens and a trimerous
gynoecium. The perianth consists of two outer (0), one intermediate or
transitional (T) and two inner tepals (I). The transitional tepal links the outer
whorl with the inner and is made up of two halves (third and sixth tepal) which
are fused (Geitler, 1929; Vautier, 1949; Galle, 1977).
The stamens are mostly eight in number and inserted in two whorls, although
changes may occur through increase or reduction. The outer whorl consists of
five stamens; four lie in pairs opposite the outer tepals and one against the
transitional. The inner whorl consists of three stamens which lie against the
carpels. The use of the term 'whorls', although technically incorrect, is
convenient to describe the flower.
Stamen number and insertion is of great importance in understanding the
Dammer (I 893)
Roberty &
Vautier (1964)
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Rheae
Koenigiinae
Polygoneae
Atraphaxidae
Atraphaxidae
Atraphaxidae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Calligoneae
Calligoneat·
Polygoneae
Polygoneae
Haraldson (1978)
Polygoneae
Persicarieae
Persicarieae
Polygoneae
Ronse Decraene
Polygoneae
Persicarieac
Persicarieae
Persicarieae
Coccolobeae
Coccolobeae
Polygoncae
Persicarieae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Polygoneae
Coccolobeae
Persicarieae
Polygoneae
Polygoncae
Polyguneae
Polygoneae
Polygoneae
Persicarieae
326
L.-P. RONSE DECRAENE AND J. R. AKEROYD
position and relationships of taxa (Ronse Decraene & Smets, 1987). The
Polygonaceae are a complex family characterized by a variable number of
stamens. The androecium is basically polymerous, with dicycly, monocycly,
obmonocycly or secondary polyandry as character states (Ronse Decraene &
Smets, 198 7). However, most taxonomic descriptions remain vague about this
matter. Stamen number has only been studied in relation to the theory of the
primitiveness of the polygonaceous flower (Gross, 1913b; Bauer, 1922; Jaretzky,
1925; Geitler, 1929; Edman, 1929; Vautier, 1949; Laubengayer, 1937). Galle
( 1977) stressed the importance of this character, attributing higher numbers of
stamens, as in Symmeria or Calligonum, to a secondary increase by 'dedoublement'
or splitting (see also Leins, 1971, 1975; Ronse Decraene & Smets, 1987).
As it is generally believed that a lost organ can never be regained by the same
developmental pathway, variation in stamen number has been associated with
changes in symmetry, fusion and dedoublement. Less attention has been paid as
to whether reductions occur in the outer stamen whorl or the inner and if these
trends are taxonomically important. The insertion of the stamens on the
receptacle can vary accordingly, as well as the length of the filaments between
the inner and outer whorl (Gross, 1913b).
In the past there has been a fair amount of controversy about the nature of
TABLE 3. The main divisions within the Polygoneae; subfamilies are
underlined; tribal level is in roman script and subtribal level is in italics
Meissner
(1857}
Bentham &
Hooker ( 1880}
Dammer
(1893}
Perdrigeat
(1900)
Gross
(1913}
Subord. Polygoneae
Pterygocarpae
Rhabarbeae, Calligoneae
Apterocarpae
Ceratogoneae, Rumiceae,
Polygoneae
Rumiceae
Eupolygoneae
Polygonoideae
Atniphaxidae
Polygon res
Polygonoideae
Polygoneae
Atraphaxinae
Oxygoninae
Subord. Brunnichieae
Coccolobeae
Triplaridae
Coccolobeae
Coccoloboideae
Co~-colobeae-
Polygoneae
Calligonees
Coccolobees
Coccoloboidcae
Coccolob~
Cocco/obinae
Antigoninea
Rumiceae
Po/y,~toninae
Jaretzky
( 1925)
Buchinger
( 1957)
Roberty &
Vautier
(1964)
Haraldson
(1978}
Polygonoideae
Rumiceae
Polygoneae
Atraphaxinae
Polygoninae
Polygonoideae
Coccolobeae
Polygoneae
Atraphaxidae
Polygoneae
Polygonoideae
Coccolobeae
Polygoneae
Polygoninae
Rumiceae
Rheae
Reynoutriinae
Polygonoideae
Persicarieae
Polygoneae
Coccolobeae
Rumicoidcae
Rumiceae
Calligonoideae
Calhgoneae
Rumiceae
Coccolobeae
327
GENERIC LIMITS IN POLYGO.NUM
the nectaries, as some authors believe the nectaries to be transformed staminodes
(Doll, 1859; Emberger, 1939), while others regard them as receptacular
outgrowths unrelated to the stamens (Eichler, 1878; Gross, l913b; Vautier,
1949; Sattler, 1973; Smets, 1986). The domination of these dual considerations
has led to the neglect of nectaries as potentially important characters. No
detailed investigation has thus so far been attempted on the floral nectaries of
the Polygonaceae, though extra-floral nectaries have received much more
attention (Schotsman, 1950) and have been shown to be of considerable
taxonomic value. Even less attention has been paid to trichomes or papillae,
which often arise in the vicinity of the nectaries of filaments. Described as "eine
Behaarung der Filamente" (Gross, l913b), "barbula" (Meissner, 1857),
"annulus pilosus" (Bentham & Hooker, 1880), etc., these have only been
investigated for their morphological value, without relation to the nectaries. We
have investigated both nectaries and trichomes or papillae as structures which
might play a role in attracting pollinators, although there is almost no mention
of them in the literature or of any potential function of the trichomes.
Tepal structure has only been dealt with extensively in relation to the
development of the fruit (Gross, 1913b; Roberty & Vautier, 1964, etc.), as
conspicuous changes occur in relation to fruit dispersal. The tepals can be
connate, or fused with the stamens in different ways. In some taxa (Polygonella,
Atraphaxis, Pteropyrum, etc.) they are almost free; in others they are extensively
Subord. Symmerieae
Triplaridae
Triplaridae
M uehlenbeckiees
Triplareae
Gymnopodinae
Triplarinae
Triplareae
Subord. Eriogoneae
Eriogoneae
Rumicoideae
Eriogoneae
Rumicees
Eriogoneae
Eriogonoideae
HoJhsterieae
Eriogoneae
( Eriogonoideae)
Triplaridae
Eriogonoideae
Eriogoneae
(Eriogonoideae)
Triplareae
Rumiceae
Erioaonoideae
Hollisteneae
Triplareae
Antigoneae
Koenigieae
328
L.-P. RONSE DECRAENE AND J. R. AKEROYD
fused (Polygonum section Polygonum, Polygonum section Persicaria). The
differentiation of the inner and outer whorl can be slight or very strong: some
attention will be paid to these phenomena. Reductions of the outer or inner
whorl could occur separately and also have some taxonomic importance. Floral
anatomy in the Polygonaceae has been investigated by Laubengayer ( 1937)
using floral sections, and Vautier ( 1949) using different clearing techniques on
whole flowers. Their studies were more concerned with explaining the inherent
structure of the flower than with systematic considerations. However, Vautier
( 1949) indirectly demonstrated that it was possible to delimit taxonomic groups
on the basis of the vasculature of the flowers, especially that of the tepals.
Attention is paid to the vasculature of the tepals as well as to the epidermal
surface (shape of cells and cuticle). The cuticle is considered to be of some
interest in classification (Fahn, 1974) being variably rough, smooth, ridged or
furrowed. However, Fahn does not refer to the tepa! cuticle. For comparative
purposes only the upper adaxial surface of the inner tepals has been
investigated, as the epidermal cells can vary in shape and texture on different
parts, or between the inner and outer tepals (see Geitler, 1929; Vautier, 1949).
Several previous authors have investigated the subgeneric relationships of
Polygonum sensu lato using different characters. We have investigated less
conventional floral characters that have escaped attention or have been rejected
as unimportant, and we shall try to correlate the results with data derived from
other systematic disciplines.
MATERIAL AND METHODS
This investigation included 83 species from different sections of Polygonum sensu
lato (see Appendix 1), as well as from the related genera Atraphaxis, Polygonella,
Oxygonum, Koenigia, Fagopyrum, Harpagocarpus, Pteropyrum and Calligonum. We
studied representatives of all the sections considered by Meissner ( 1857) under
Polygonum L. (section Aconogonon, Amhlygonon, Cephalophilon, Bistorta, Echinocaulon,
Persicaria, Tiniaria, Avicularia and Tephis) as well as those described later by
different authors (Pleuropterus, Duravia, Pseudomollia, Tovara). We did not
examine section Pseudopolygonella Benth. & Hook. or section Eleutherosperma
Hook., but have treated the former under Polygonella and the latter under
Koenigia.
Specimens were either collected fresh in Bruges, Belgium, cultivated plants or
weeds from L.-P.R.D.'s garden, or were gathered from the botanic gardens at
Kew, Brussels, and the Universities ofOxford and Reading. The floral material
was preserved in formalin-acetic acid-alcohol (FAA). Floral samples of
Reynoutria sachalinensis, preserved in alcohol, were sent by J. P. Bailey from the
University of Leicester. Other specimens were taken from herbarium sheets at
Reading (RNG) and Kew (K). Material was soaked in warm water and
examined by dissecting, light and scanning electron microscopes. The flowers
were dissected and drawn as accurately as possible. A number of flowers were
also cleared in warm 5% sodium hydroxide solution, bleached in sodium
hypochlorite for 5 minutes, soaked in water and stained in saffranin. The flowers
taken for SEM observation were osmicated using an osmium tetroxide (Os0 4 )solution for up to two hours. The specimens were washed in water and
dehydrated in acetone for four hours, changing concentrations every half hour,
GENERIC LIMITS IN POLrGONUM
329
and were left in 100% acetone overnight. The next day, Critical Point Drying
was carried out, using a CP-Drier. The specimens were mounted on stubs and
coated with a 30 ~l.m layer of gold before being studied under a Jeol T-20 SEM
fitted with a Mamiya camera.
RESULTS
(see Appendix 1)
To avoid confusion by the use of segregate genera, all species of Polygonum
sensu lato are listed in Appendix 1 as Polygonum L. under their respective tribes
following the classification of Meissner (1857). At least 4-10 flowers were
studied for each species. The number of species was too large to make a
thorough investigation of numerous specimens from different origins (see
Appendix 2). Especially for those functionally dioecious species (section
Aconogonon and section Tiniaria), male and female flowers are morphologically
different (Conolly, 1977; Conolly, personal communication). At the time of
study no sufficient material of both sexes was available. In some cases
investigations had to be limited to male-sterile flowers, which reduced the scope
of the observations made. These species are marked with an asterisk in
Appendix 1.
On the other hand, the large number of species investigated is a reasonable
counterbalance to the extremely limited number of specimens examined, as only
supraspecific characters were taken in consideration, which tends to reduce
intraspecific variability and consequent errors.
The characters on the tables were selected for their significance and may be
added to data from other disciplines as will be discussed later.
Tepa! venation types are related to the manner of branching of the tepa! veins
and are essentially trifid or consist of one single main vein.
The external tepa! morphology refers to the shape, fusion and size of the
peri an th parts.
Secondary ramifications of the main veins include further branching and
anastomoses.
The cells of the tepa! epidermis were found to be of some taxonomic
importance. Their shape and size as well as the sculpturing of the cuticle have
been taken into account.
Floral formula is of importance in determining possible trends in the number
of parts within the flower, as well as within different organs of the flower.
Numbers in brackets refer to occurring variabilities and are not constant
features.
The stamens were included as a character of importance: filament
morphology must be taken with some reservation as to the shape, except for the
base. Anthers and the epidermis were not included as few differences were
found.
The insertion of the stamens, i.e. their relation to other floral parts, fusion,
divergence between whorls and position of the nectaries have been found to be
of importance.
The size, shape and fusion of nectaries have been investigated, as well as the
associated papillae or trichomes.
330
L.-P. RONSE DECRAENE AND J. R. AKEROYD
No characters of the gynoecium were included. However, data from the
literature have been taken into account.
The data in Appendix 1 are not complete as other less significant characters
were omitted.
DISCUSSION
The generic approach
From the results of this study, and comparison with the literature, the
following generic scheme is proposed within the subfamily Polygonoideae.
Investigated species, together with new combinations, are listed in Appendix 2.
1. Tribe Persicarieae
Persicaria Mill. ( 1754)
SYNONYMS:
Polygonum L. section Persicaria (Mill.) Meissn. ( 1826) pro parte.
Goniaticum Stokes ( 1812)
(Including sections Bistorta, Persicaria, Aconogonon and Tovara.)
Uniting Persicaria with Polygonum sensu stricto is unnatural, and indeed, cuts
across the unique affinities of both taxa. Their apparent resemblance can only
be linked by their more distant affinities within the subfamily Polygonoideae.
On the basis of the floral characters listed below, Persicaria is best maintained as
a distinct genus, and separated from Polygonum sensu stricto. Other diagnostic
characters are mentioned in the literature, including pollen morphology,
anatomy, chemistry and gross morphology (Gross, 1913b; Hedberg, 1946;
Haraldson, 1978; Stanford, 1925a, b). The following floral characters are
significant as well:
I. The outer tepals are never keeled or angular in Persicaria, and do not differ
much from the inner tepals, except in size (see also Graham & Wood, 1965).
2. The tepal vasculature is of a distinct type (trifid venation), different from the
generalized dendricular venation of Polygonum (Figs 1, 2 10).
3. The tepal epidermis is of a different type in Persicaria, rectangular cells with
straight to sinuate anticlinal walls and longitudinal striae (Figs 13, 17).
4. The species of Persicaria have interstaminal, free or fused nectaries, which
do not occur in Polygonum (Figs 1, 2, 3, 12, 14, 16, 18, 19). Papillae are always
situated on the receptacle in close proximity of these structures.
5. The filaments are never flattened and strongly subulate as in Polygonum, but
are often cylindrical and filiform (Figs 19, 18, 2, 1).
Persicaria has been defined by Gross ( 1913a, b) in a broad sense to include
several sections, except Bistorta and Pleuropteropyrum. Other authors (Jaretzky,
1925; Hedberg, 1946; Hara, 1966; Haraldson, 1978) have split the genus but do
not agree on which taxa should be included.
We maintain Persicaria as a natural unit, containing four sections: Tovara,
Bistorta, Aconogonon and Persicaria. Section Persicaria includes Amblygonon,
Echinocaulon and Cephalophilon, as the characters used to differentiate these groups
are not clear enough and their use damages the integrity of other taxa as
sections under Persicaria.
GENERIC LIMITS IN POLrGONUM
331
',
3
0.6 mm
5
0,25mm
0.3mm
Figures 1-6. (0 =outer; I= inner; T =transitional). Fig. I. Persicaria minor (Huds.) Opiz; flower,
cut open. Note four tepals with loss of a transitional. Fig. 2. Persicaria diuaricata (L.) Gross; flower,
cut open, nectaries fused into a ring. Fig. 3. Persicaria uirginiana (L.) Gaertn.; flower, cut open;
anthers removed. Fig. 4. Fagopyrum dihotrys (D. Don) Hara; flower, cut open. Fig. 5. Koenigia
nummurlarifolia (Mt'issn.) Mesicek & Sojak; flower, cut open. Note papillar zones. Fig. 6.
Harpagocarpus snowdenii Hutch. & Dandy; flower, cut open.
Haraldson ( 1978) believes that the genus Persicaria is highly advanced in her
tribe Persicarieae, mainly on the basis of the trichome structure, pollen,
cleistogamy, heterostyly, entogamy and nectaries. The inner stamen whorl ts
also reduced; the carpels are dimerous, and the tepals are usually fused.
a. Section Persicaria (Mill.) Gross (1913)
(Including section Cephalophilon Meissn. in Wall. ( 1832), section Amblygonon
Meissn. ( 1826), section Echinocaulon Meissn. in Wall. ( 1832).)
332
L.-P. RONSE DECRAENE AND j. R. AKEROYD
0.7 mm
9
0
10
0,6mm
I.Omm
II
mm
Figures 7··II. (0 =outer; I inner; T =transitional). Fig. 7. Pofygonum patulum Bieb.; flower, cut
open. Note fusion of transitional and inner tepals. Fig. 8. Oxygonum delagoense Kuntze; flower, cut
open, gynoecium and filament bases. Fig. 9. Calligonum tetrapterum Jaub. & Spach; flower from
above, gynoecium removed. Fig. 10. Fagopyrum giraldii (Damm. & Diels} Haralds.; outer tepa),
vasculature. Fig. 11. Fallopia baldschuanica (Regel} Holub; inner tepal, vasculature.
The section is clearly differentiated from others by several characters:
I. The outer stamen whorl is always inserted above the inner on the fused
receptacle (Fig. I).
GENERIC LIMITS IN POLYGOJIUM
333
Figures 12~17 . Fig. 12. Persicaria maculata (Raf.) Love & Love; nectary with papillae. Scale
bar= 50 J.lm. Fig. 13. Pmicaria capita/a (Ham.-Buch. ex D. Don) Gross; inner tepal surface. Scale
bar= 10 J.lm. Fig 14. Pnsicaria perfoliala (L.) Gross; inner filament base, nectarics and papillae.
Scale bar= 66J.1m. Fig. 15 . Pmicaria uacciniifolia (Wall. ex Meissn .) Ronsc Denat'ne; thickened
filament base (inner stamen ). Scale bar= 50 J.lm. Fig. 16. Persicaria amplexicaulis (D. Don ) Roose
Dccraene; nectary and filament bases. Scale bar= 66 J.lm. Fig. 17. Pmicaria polyslachya (Wall ).
Gross; inner tepa! surfact'. Scale bar = 6 J.lm.
2. Reductions occur in the inner and transitional stamen and tepa) whorls and
are often characteristic for a species (e.g. P. amphibia, P. hydropiper; see also Trail,
1896; Stanford, 1925a; Fig. I).
334
L.-P. RONSE DECRAENE AND J. R . AKEROYD
Figures 18-23. Fig. lB. Persicaria polystachya (Wall.) Gross; inner stamens and ovary. Scale
bar= 100 j.lm. Fig. 19. Persicaria angustifolia (Pall. ) Ronse Decracne; Hower from above; filaments
and ovary. Scale bar= 200 j.lm. Fig. 20. Persicaria campanulata (Hook. F.) Ronsc Decraene; lateral
view of flower; gynoecium and anthers removed, tepals reHexed (functionally female Hower). Note
papillae on receptacle. Scale bar = 285 11m. Fig. 21. Koenigia forrestii (Diels) Hedb.; inner filaments
with disc and papillae. Scale bar= 100 j.lm. Fig. 22. Koenigia pilosa Maxim.; Papillae. Scale
bar= 6j.lm. Fig. 23 . Po[ygonum aviculart L.; inner stamen. Scale bar= 100 11m.
3. The anthers are ovate, small and inserted on a filiform filament. The inner
filaments are longer than the outer and are often as long as the strongly fused
perianth (Fig. 1).
GENERIC LIMITS IN POLrGONUM
335
4. The nectaries are obvious, free, globular structures with numerous papillae
on the back or higher up the receptacle (Figs 1, 12, 14).
5. The tepa! epidermis is of a same type, rectangular cells with straight
anticlinal walls and longitudinal striae (Fig. 13).
6. The tepa! vasculature is of the trifid type, but the number of ramifications is
low (Fig. 1).
Anomalous nectaries occur in Persicaria chinensis and P. runcinata (see
Appendix 1), where they are fused into a disc-like structure as in section
Aconogonon. In Persicaria sieboldii the shape is unique, i.e. rectangular.
The sections Echinocaulon and Cephalophilon were originally distinguished from
each other and from the rest of Persicaria on the basis of the capitate
inflorescence (Meissner, 1857), and in the case of Echinocaulon on the recurved,
spine-like trichomes and has tate or sagittate leaves (Harald son, 1978). They
have been treated as separate genera or sections (Gross, 1913a; Steward, 1930;
Roberty & Vautier, 1964; Hara, 1966; Haraldson, 1978) or united as a single
taxon, Cephalophilon, mainly on the inflorescence and habit (Dammer, 1893;
Bentham & Hooker, 1880; Danser, 1927). Differences from section Persicaria are
not great, and the inclusion of other characters breaks down any clearcut
distinction, especially in the Asiatic species (Hedberg, 1946).
Meissner ( 1826) created the section Amblygonon and distinguished it from
section Persicaria on the basis of the incumbent, as opposed to accumbent,
cotyledons. Several authors have rejected Amblygonon as these distinctions have
been shown to be variable (Danser, 1927; Steward, 1930). In the characters that
we have studied, no difference could be found between this section and section
Persicaria, except for the stamen number, which was constantly seven.
b. Section Bistorta (Mill.) Jaretzky (1925) (nom. illeg.).
Polygonum L. section Bistorta (Mill.) D. Don (1825).
Bistorta Mill. ( 1754).
Polygonum L. section Persicaria subsection Bistorta Benth. & Hook. ( 1880).
Colubrina Mon tad on ( 1856).
SYNONYMS:
Several authors have accepted Bistorta as a distinct genus on the basis of
several characters, such as the unique anatomy, habit, pollen, spike-like
inflorescence, divided perianth and eight stamens (Greene, 1904; Gross, 1913b;
Hedberg, 1946; Hara, 1966; Haraldson, 1978). We do not disagree with the
distinctness of the group, as several characters studied are constant and
characteristic:
1. The tepa! epidermis has elongated to rectangular cells, with undulating
longitudinal striae.
2. The stamens are very long and, like the tepals, erect and mostly free
(Fig. 15).
3. The nectaries at the base of the inner stamens are more or less united with
the bases of the filaments and not distinct; the outer nectaries are sometimes
absent (Figs 15, 16).
4. Papillae are often few in number or not developed, and occur in folds behind
the nectaries (Fig. 15).
336
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
On the other hand, recognition at generic rank is perhaps excessive, as several
characters are shared by section Persicaria, such as the pollen and the
inflorescence (Jaretzky, 1925). There is also the same trifid tepa! vasculature,
comparable epidermal cells, filiform stamens with occasional reductions, the
same shape and position of the nectaries (though fusion is more advanced in
section Bistorta) and the same type of papillae in association with the nectaries.
A stronger relationship for section Bistorta is found with section Aconogonon
within Persicaria: the pollen is of the same tricolpate type (seejaretzky, 1925; the
distinction made by Hedberg is not great enough to merit generic rank); the
outer stamens are not inserted much above the inner, as is the case in section
Tovara and Persicaria, and the nectaries sometimes have the appearance of a
fused disc. J aretzky ( 1925) also linked section Bistorta with section Aconogonon on
the basis of the inflorescence and chemical affinities (antrachinones). The
similarity in habit may be associated with the distribution of the section in
Arctic and subalpine regions of the world. Several of the specimens that we
examined also showed anomalies in structure, probably due to the extreme
environmental conditions. The reduction of the nectaries and loss of papillae may
be linked with this phenomenon, as well as with a lack of pollination vectors in
these colder regions.
c. Section Tovara (Adans.) Gross (1913)
Tovara Adans. ( 1763).
Antenoron Raf. ( 181 7) .
Sunania Raf. (1837).
Polygonum L. section Persicaria Meissn. (1857), pro parte.
SYNONYMS:
The identity of section Tovara is unambiguous. Previous authors have
accumulated evidence for its recognition as a distinct taxon, such as the
persistent hooked style, which is bifid to the base, the five stamens and the
perianth, which is unequally four-partite and scarcely enlarged in fruit (Li,
1952; Holm, 1927), the distinct pollen (Hedberg, 1946) and disjunct, relict
geographical distribution. Persicaria filiformis occurs only in Asia, and P.
virginiana is only found in North America (the two species are united by many
authors). Those who recognize Tovara at generic rank often base their
conclusions on this evidence (Li, 1952; Steward, 1930; Hara, 1962, 1966;
Roberty & Vautier, 1964).
However, Haraldson ( 1978) showed that deeply bifid styles also occur in a
number of taxa in section Persicaria. The pollen is distinct, but can be seen as a
continuum with Persicaria, through P. amphibia as an intermediate form
(Hedberg, 1946; Haraldson, 1978). Holm (1927) demonstrated that flowers
with six stamens occur as well in P. virginiana, which refutes the idea of a
constant five-partite androecium in the section. There is some other evidence
that demonstrates a continuum with Persicaria section Persicaria:
1. The tepa! epidermis is quite distinct, although resembling the basic type
found in Persicaria.
2. The unequal tetramerous perianth is not unique, as several species of
Persicaria have smaller outer tepals, or only four tepals (Figs 1, 3), though this
state is less constant (e.g. Persicaria senegalensis, P. peduncularis, P. lapathifolia,
P. minus, etc.).
GENERIC LIMITS IN POLrGONUM
337
3. The nectaries are large, distinct and acute, but do not differ in position and
structure from those of Persicaria (Fig. 3). Papillae are few or absent.
We maintain Tovara as a section of Persicaria. Evidence for an early
differentiation of the section lies in its disjunct distribution, as well as in the
specialized nut morphology, which is linked with a specialized dispersal
mechanism (Graham & Wood, 1965; Haraldson, 1978).
d. Section Aconogonon (Meissn.) Gross 1913
SYNONYMS: Polygonum L. Section Aconogonon Meissn. ( 1826).
Aconogonum (Meissn.) Reichenb. (1837).
Gononcus Raf. ( 183 7).
Aconopogon Nakai ( 1922).
Pleuropteropyrum Gross ( 1913), pro parte.
Ampelygonum Lindl. ( 1838), pro parte.
Eight to ten species of section Aconogonon (Meissner, 1826, 1857) have been
investigated. All share a number of features which clearly separate the group
from other taxa:
I. The tepals showed a trifid venation in all cases (Fig. 2), which often ramifies
into long secondary veins (see also Vautier, 1949: 251).
2. The tepa! surface consists mainly of rectangular cells, with a smooth or
slightly striate cuticle (Fig. 17). P. campanulata has a strongly ridged cuticle.
3. The stamens are mostly eight in number; the outer are sometimes shorter and
reductions occasionally occur in the inner whorl (Figs 2, 18, 19, 20). The
filaments are stout and cylindrical, inserted at about the same level or the outer
are slightly higher (Figs 18, 19), but not, as in section Persicaria distinctly higher.
A higher insertion of the outer whorl is due to fusion with the tepals (e.g.
P. campanulata).
4. The nectaries are conspicuous, but fused basally into a prominent disc-like
structure confluent with the bases of the stamens (Figs 18, 19, 20).
5. Papillae are numerous and inserted behind the nectaries or spreading on the
receptacle (Figs 18, 19).
6. There is a clear tendency towards dioecy, with functionally male and female
flowers on different plants (Conolly, 1977; Conolly, personal communication;
Lousley & Kent, 1981), e.g. P. polystachya, P. weyrichii, P. campanulata.
We maintain Aconogonon as a section of Persicaria despite arguments in favour
of segregating it at generic rank (see also Hedberg, 1946; Hara, 1966;
Haraldson, 1978). Hedberg mentions the creeping rhizomes, very short styles
and capitate stigmas as distinctive characters, as well as the pollen (Aconogonontype). We have found taxa with longer styles (e.g. Persicaria polystachya), as
already observed by Webb & Chater (1963); this is related to the occurrence of
heterostyly (Conolly, personal communication). On the other hand, several
characters link sect. Persicaria with section Aconogonon (see under section
Persica ria).
Different authors have not circumscribed the section similarly. Gross ( 1913)
lumped Persicaria pawlowskyana, P. weyrichii and P. tripterocarpa into a single genus
Pleuropteropyrum, mainly on the basis of the winged achene. Bentham & Hooker
(1880) put P. Weyrichii into their section Pleuropterus, together with Polygonum
338
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
cuspidatum, P. multifiorum and P. sachalinense. Persicaria weyrichii is aberrant through
its lack of keeled outer tepals and its very different stamen, stigma and nectarial
morphology. Roberty & Vautier (1964) agree with the general resemblance of
P. weyrichii to section Aconogonon, but keep it separate, together with P. Molle, in
the genera Ampelygonum Lindl. and Pleuropteropyrum Gross on the basis of the
different fruit morphology. We found that P. weyrichii is linked by several
obvious characters to section Aconogonon, such as tepal epidermis, the fused disc
and the pollen.
Persicaria polystachya has been separated from the genus Aconogonon by Hara
( 1966) into his section Persicaria, on the basis of the distinct pollen morphology.
We must challenge this view, as the species is very close morphologically to
other species of section Aconogonon (e.g. P. angustifolia) and aberrant in section
Persicaria. The treatment here follows that of other authors (Hedberg, 1946;
Haraldson, 1978), who have used different lines of evidence. Persicaria
campanulata resembles the genus Koenigia in a number of characters, such as the
loss of nectaries as separate entities, the grouping of papillae in conspicuous
fields and the strongly ridged tepal epidermis. However, only male-sterile
material was used, and the suggestion that this species is intermediate between
Persicaria and Koenigia needs further investigation.
Koenigia L. ( 1767) emend. Hedb.
SYNONYMS: Polygonum section Koenigia (L.) Hook. ( 1890), pro parte.
Maconastrum Small ( 1891), nom. illegit.
Polygonum section Eleutherosperma Hook. ( 1890), pro parte
Polygonum section Cephalophilon Meissn. ( 1857), pro parte.
Defined by Linnaeus ( 176 7) as containing a single species (Koenigia islandica),
the position of this genus was for a long time a matter of debate.
Hooker ( 1886) placed Polygonum delicatulum and P. filicaule in his section
Eleutherosperma.
On the basis of the similarity of the pollen, Hedberg ( 1946) placed these
species, together with P. nummularifolium and P. forrestii into the genus Koenigia.
Previously Meissner ( 185 7) had put P. nummularifolium, P. delicatulum and
P.filicaule into his section Cephalophilon, but Hooker (1886) placed
P. nummularifolium in section Aconogonon.
From a study of the six species aggregated by Hedberg ( 1946), it is concluded
that the genus, as defined by him, is a natural grouping clearly differentiated
from other taxa (Ronse Decraene, in press). A number of characters link the
species:
1. The epidermal cells of the tepals are rectangular, with a sinuate outline and
deep longitudinal striae.
2. The nectaries form a conspicuous central disc. The papillae are of a different
type from other genera (Figs 21, 22), with a club-like head.
3. The genus shows a tendency towards trimery, by the fusion or suppression of
the outer tepals.
4. The tepal venation is simplified to an unbranched trifid structure (Fig. 5).
The observed characters support fully the independence of Koenigia (see also
Hedberg ( 1946) for other characters). Haraldson ( 1978) relates Koenigia to
Aconogonon on the basis of the similar trichome type, as well as the form of the
GENERIC LIMITS IN POLYGONUM
339
inflorescence. We prefer to associate Koenigia with Persicaria section Aconogonon
for several other reasons:
l. Both taxa occur mostly in the same geographical area (eastern Asia).
2. The echinate pollen of Koenigia could be derived from the smoother pollen of
section Aconogonon. Persicaria hookeri has pollen with small spinules.
3. The more primitive members of Koenigia (e.g. K. forrestii) have a welldeveloped disc around the inner stamens (Fig. 21). The papillae are inserted in
zones between the stamens, as in some members of Persicaria. There is a
progressive reduction in the number of papillae from many (Koenigia forrestii,
Fig. 21) to few (K. delicatula, K. pilosa, Fig. 22).
4. The insertion of the outer stamens in Koenigia is seemingly higher, but they
arise at the base of the disc. A similar fusion occurs in Persicaria campanulata.
5. The epidermal cells of the tepals are comparable. Both are rectangular, with
longitudinal striae.
Thus we believe Koenigia to be an extreme evolutionary form of Persicaria
section Aconogonon. The same treatment is followed by Haraldson ( 1978: 65) in
her putative diagram of relationships.
Fagopyrum Mill. ( 1754)
SYNONYMs: Polygonum Adans. (I 763).
Helxine 0. Kuntze (1891).
Fagopyron Rafin. ( 1837).
Phegopyrum Petermann ( 1841), nom. nud.
Kunokale Rafin. (1837).
Polygonum L. section Fagopyrum Meissn. (1826).
Several characters support the acceptance of this genus as distinct: the
petaloid tepals, which are not accrescent in fruit, the flattened filaments with a
flap-like appendage, the free, globular and stalked nectaries with few papillae,
and the large oblong to ovate anthers. Other characters include the distinctive
pollen, mature fruits, constant stamen number, hastate, triangular leaves,
chemistry (protofagopyrin and fagopyrin: Haraldson, 1978) and chromosome
number (n = 8: Mahony, 1935;Jaretzky, 1928). Most authors accept Fagopyrum
as a genus close to Polygonum sensu lata (Bentham & Hooker, 1880; Dammer,
1893; Hedberg, 1946; Tutin, 1964; Haraldson, 1978).
Dammer & Diels ( 1905) described a new genus, Pteroxygonum with one species,
P. giraldii on the basis of the particular type of nut (with dentate and winged
angles). Gross (1913a), Hedberg (1946),Jaretzky (1925) and Roberty & Vautier
( 1964) accepted it as a genus as well, though Hedberg thought Pteroxygonum to
be more closely related to Fagopyrum than to any other taxon, on the basis of the
similarity in pollen morphology. Haraldson ( 1978) showed that Pteroxygonum
could not be maintained as a distinct genus, but had to be considered as one
extreme within the range of variation in Fagopyrum for intermediate characters
occur. Its maintenance as a species of Fagopyrum is not discussed, as we found a
similar morphology. Morphological characters are better for explaining the
affinities of Fagopyrum than for its exclusion as a taxon. The mature nut has been
used as an important distinctive character. According to Roberty & Vautier
(1964) this character does not separate the group, as it is similar to some species
340
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
in section Aconogonon. The classic opinion about Fagopyrum is that it is closely
related to Fallopia (Gross, 1913a, b), mainly because of the similar habit.
Haraldson (1978) found a similarity in the petiole anatomy, but related it to the
similar life-form. We do not support the relationship of both genera, either on
the stamen morphology, or the vasculature of the tepals and nectaries, which
are completely different. Moreover, the inner stamens are extrorse in Fagopyrum
and introrse in Fallopia. Fagopyrum is probably closely related to Persicaria. The
trifid venation of the tepals and epidermal cells are almost comparable
(Fig. 10). The same type of nectaries and short, smooth papillae are found in
both genera; they closely resemble those found in section Persicaria. Both taxa
have non-angular outer tepals, filaments which do not expand at the base
(Fig. 4) and inner extrorse and outer introrse stamens. Fagopyrum probably
represents a putative ancestral flower-type for Persicaria and its relatives. The
stamen number is constantly eight, the stamens alternate with free and
conspicuous nectaries, the tepals are almost free and petaloid. Miege ( 191 0)
links the flower with that of Rheum: "duquel il ne differe que par l'avortement
d 'un sepale et d'une etamine correspondante".
Ha.rpa.goca.rpus Hutch. & Dandy (1926).
One species: H. snowdenii Hutch. & Dandy
This monotypic genus has been described comparatively recently from East
Africa, on the basis of the fruit morphology. Our observations of Harpagocarpus
indicate a strong resemblance to Fagopyrum, as the morphology is very similar
(nectaries, stamen insertion, tepal epidermis; Figs 4, 6).
The pollen of Fagopyrum is ovate, tricolpate with narrow furrows and a
reticulate surface pattern. We observed an identical pollen structure in
Harpagocarpus.
We do not agree with the taxonomic position suggested by Haraldson ( 1978),
that is to place this genus close to Fallopia. The presence of nectaries, stamen
morphology, tepal surface and venation argue against this view. On the basis of
these characters, and taking the great variability of the pistil morphology in
Fagopyrum, Harpagocarpus should probably be included within Fagopyrum, perhaps
as a separate section.
2. Tribe Polygonea.e
Polygonum L. (1753)
Cnopos Raf. ( 183 7).
Pleurostena Raf. ( 183 7).
Avicularia J aretzky ( 1925), nom. illeg.
(Including section Avicularia and section Tephis.)
Section Polygonum contains P. aviculare L., the type species of the genus. The
genus forms an obvious natural unit, characterized by a large number of
features:
SYNONYMS:
I. The outer tepals are often differentiated from the inner, smaller and pointed
or slightly angular around the single main vein (Fig. 7).
2. The tepa) epidermis is similar in most species investigated, consisting of
irregular, elongated cells with sinuate outline. The cuticle is often deeply and
irregularly ridged (Fig. 24).
GENERIC LIMITS IN POLYGO.NUM
341
Figures 24-29. Fig. 24. Polygonum aviculart L.; inner tepal surface. Scale bar = 10 ~tm. Fig. 25.
Polygonella articulata (L.) Meissn.; inner tepal surface. Scale bar= 10 ~tm. Fig. 26. Fallopia japonica
(Houtt.) Ronse Decraene var. compacta (male-sterile). Flower from above, ovary removed. Scale
bar= 200 ~tm. Fig. 27. Fallopia baldschuanica (Regel) Holub; filament bases with trichomes. Scale
bar= 100 ~tm. Fig. 28. Pleropyrum scoparium Jaub. & Spach; flower from above, a stigma removed.
Scale bar = 200 ~tm. Fig. 29. Atraphaxis huxifolia Jaub. & Spach; flower, lateral view, ovary
removed. Scale bar = 285 ~tm.
3. Only one main vein is present in each tepal (the transitional sometimes has a
supernumerary smaller vein). The vascular bundle often branches in a
dendricular manner (Fig. 7).
4. The inner stamens are larger than the outer and have a swollen, dilated
342
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
Figures 30, 31. Fig. 30. Atraphaxis spinosa L.; flower from above. Note paired outer stamens. Scale
bar= 20011m. Fig. 31. Cal/igonum microcarpum Barszcz.; flower from above. Note G4, All-12. Scale
bar= 2851!m.
filament base. All filaments are flattened (Figs 7, 23). The anthers are ovate and
small in comparison to the filaments.
5. The outer stamens are often reduced or disappear altogether, but not the
inner ones (Fig. 7; see also Trail, 1896).
6. No nectaries are visible; perhaps a layer of cells at the base of the filaments
secretes nectar.
We distinguish two sections in Polygonum, although by comparison with
Persicaria their boundaries are not clear, due to the high level of variability
within the genus.
a. Section Po(ygonum
Avicularia Meissn. ( 1826).
(Including section Pseudomollia Boiss. (1879), section Duravia S. Wats. (1873).)
SYNONYM:
Some authors accept a further division of Polygonum into a number of sections
(Polygonum, Pseudomollia, Tephis and Duravia), mainly on the basis of characters
which have been shown to be of little discriminant value. Watson ( 1873)
separated his section Duravia, with one species (P. californicum), from section
Polygonum on the basis of differences in the achenes. Greene ( 1904) included a
few other species in his genus Duravia on the basis of some vague morphological
characters. Section Duravia has recently been accepted by a number of authors
(Hedberg, 1946; Haraldson, 1978; Hickman, 1984). The three specimens that
we studied are similar to each other in a number of features, such as the tepal
vasculature, and filament and anther morphology. On the other hand, no real
distinction of importance could be found in comparison with section Polygonum.
The tepal epidermis is wholly comparable (e.g. P. scoparium versus P. douglasii)
as is the stamen morphology. Both have dilated, flattened filaments without
visible nectaries, and small ovate anthers. The only important differences are
found in the pollen, which is comparable to Polygonella (see under that genus)
and the petiole anatomy (see Haraldson, 1978).
We do not consider these characters, as well as some other minor features, to
be important enough to merit sectional rank, especially if compared with those
given for the sections of Persicaria. Moreover, Polygonum section Polygonum shows
GENERIC LIMITS IN POLYGONUM
343
a great inherent variability, which is compatible with changes in morphology.
The taxonomy of North American species remains confused, as different
populations tend to show wide gene-flow and a high level of interbreeding
(Mertens & Raven, 1965; Wheeler, 1935). It is better to describe them under
the variability of Polygonum section Polygonum.
Polygonum molliaiforme was accorded sectional rank by certain authors
(Bentham & Hooker, 1880; Dammer, 1893; Hedberg, 1946) on the basis of a
number of characters which Haraldson ( 1978: 79) considers to be the result of
the reduced growth habit. We found P. molliaiforme to be wholly comparable to
section Polygonum, and it does not merit separation at sectional rank.
b. Section Tephis (Adans.) Meissn. (1857)
Tephis Adans. ( 1763).
Avicularia section Tephis (Adans.) J aretzky ( 1925), nom. illeg.
SYNONYMS:
The section was erected early to contain the single species Polygonum undulatum,
mainly on the basis of the tetramerous perianth, dimerous ovary and short
internodes. It was maintained as such by Bentham & Hooker ( 1880), Dammer
(1893), Jaretzky (1925), Hedberg (1946), Roberty & Vautier (1964) and
Haraldson ( 1978). The last author included P. afromontanum in the section on
the basis of anatomical similarities. We have maintained section Tephis on the
basis of characters found in Polygonum afromontanum, but unfortunately we were
unable to investigate P. undulatum to confirm these observations.
The characters that distinguish this section are:
I. The outer tepals have a well-developed keel, as in Fallopia; those of other taxa
within Polygonum are at most angled.
2. The main tepa! vein develops two laterals, which are inserted at different
heights.
3. The tepa! epidermis is different, consisting of rectangular to elongated cells
with an almost longitudinal striation.
Further evidence is provided by the restricted geographical distribution (some
Afro-montane regions), the anatomy (Haraldson, 1978), pollen (Hedberg, 1946),
and the almost horizontal styles. The link with section Polygonum nevertheless
remains very strong, and its value as a section is uncertain.
Polygonella Michx. ( 1803).
Lyonia Raf. ( 1808).
Phyllepidum Raf. ( 1808).
Lyonella Raf. ( 1818).
Stopinaca Raf. ( 1836).
Tephis sensu Raf. ( 1836) non Adans.
Gonopyrum Fisch. & Mey. (1845).
Thysanella A. Gray (1845).
Delopyrum Small ( 1913).
Psammogonum Nieuwl. ( 1914).
Dentoceras Small ( 1924).
SYNONYMS:
Polygonella has been a controversial genus since the time of Linnaeus, as it has
been either ignored or its importance has been exaggerated. Meissner ( 1857)
344
L.-P. RONSE DECRAENE AND J. R. AKEROYD
placed the genus in a different subtribe, Ceratogoneae, but later authors
recognized it as being not very distinct from Polygonum sensu lato.
Subgenus Polygonella is generally recognized (Horton, 1963; Graham &
Wood, 1965) as having two outer and three inner tepals; the filaments are
dilated at the base, forming two lateral teeth. It consists of eight species. We
studied four to five species from the subgenus.
Subgenus Thysanella has two outer, one transitional and two inner tepals and
the filaments are all alike. It consists of one species.
We shall not discuss the integrity of this genus, which is clearly defined by a
number of characters linking it with Polygonum:
I. The inner stamens are larger than the outer and have a widely expanded
base. The outer filaments are only slightly expanded.
2. The tepa! epidermis is in most cases similar (Figs 24, 25).
3. The outer tepals are differentiated from the inner and are often angular.
4. There is only one vein present in each tepa! (cf. Horton, 1963; Vautier, 1949;
Graham & Wood, 1965).
Further evidence is given by Horton ( 1963) and Haraldson ( 1978). Hedberg
( 1946) found that the pollen of Polygonella did not differ in the slightest from
Polygonum section Duravia, and this was confirmed in the present study. The
genus is also anatomically closer to Polygonum (Haraldson, 1978: section
Duravia). Further evidence of a close affinity is given by the similar tepa! surfaces
and the filaments, which are also dilated at the base in Polygonum. This, together
with the fact that pollen is of a greater diversity in the other Polygonaceae,
could be an argument for their inclusion in one single genus. In this case
Polygonella should be included as a section of Polygonum since section Duravia
cannot be separated from Polygonum (see under that genus). On the other hand,
several differences in habit and geographical distribution do exist. Hedberg
( 1946) believes that the same pollen type evolved convergently in Duravia and
Polygonella. We lack the evidence to extend this assumption for the affinities of
Polygonella.
Fallopia Adans. ( 1763).
Polygonum section Tiniaria Meissn. ( 1826), pro parte.
Bilderdykia Dum. (1827), pro parte.
Tiniaria Webb & Moq. (1832-1850).
Fagopyrum Mill. section Tiniaria (Meissn.) Gross (1913).
Helxine Raf. (1837), non Requien.
Polygonum L. section Helxine L. ex Hyland. (1966).
Polygonum L. section Pleuropterus Benth. & Hook. ( 1860), pro parte.
Pleuropterus Turcz. ( 1848), pro parte.
Rrynoutria Houtt. ( 1777), pro parte.
We propose to consider the genus Fallopia in a broad sense so as to include the
genus Tiniaria ( = Bilderdykia = Fallopia), as well as the genus Rrynoutria
( = Pleuropterus).
Several authors have kept Tiniaria separated from Pleuropterus (Bentham &
Hooker, 1880; Gross, 1913a, b; Roberty & Vautier, 1964; Webb & Chater,
1964; Haraldson, 1978; etc.). Webb & Chater ( 1963) give as distinctive
characters the small capitate, subsessile stigmas in Bilderdykia and the distinct
SYNONYMS:
GENERIC LIMITS IN POLYGO.NUM
345
styles, with fimbriate stigmas, in Fallopia (see also Hedberg, 1946: 398). Love &
Love ( 1956) point out the cytological dissimilarities. Holub ( 1970) considered
Rrynoutria and Fallopia as sufficiently distinct to be kept separate (habit,
character of styles and stigmas and chromosome number), and Roberty &
Vautier (1964) put the genera Rrynoutria and Bilderdykia the furthest away from
each other in different tribes, mainly on the basis of the habit and the
morphology of the ovary (Table 2).
However, many authors consider the differences to be not clearly defined, as
examples exist of species that are intermediate (Hedberg, 1946). They aggregate
the genera into one section (Danser, 1927; Steward, 1930; Graham & Wood,
1965) or genus (Jaretzky, 1925; Hedberg, 1946). Jaretzky considers that the
morphology of the stigmas and the chemistry are similar enough to consider
only one genus. Extrafloral nectaries are found in both sections (Graham &
Wood, 1964). Hedberg (1946) observed that the basic chromosome number did
not coincide with the sections described, and on the basis of pollen ( Tiniariatype) and other characters he subsumed both genera within Tiniaria.
Haraldson's distinction (Haraldson, 1978) between Reynoutria and Fallopia is
not convincing, even from the table she gives to distinguish between the genera
(Haraldson, 1978: 77). The anatomical heterogeneity of Fallopia breaks down
any clear distinction from Rrynoutria. A recent study by Bailey (1988) suggests
that hybrids between Rrynoutriajaponica and Fallopia baldschuanica occur in Britain,
which provides further evidence to unite these genera. Gross ( 1913a, b)
amalgamated section Tiniaria and Fagopyrum. This is rather unnatural, as
Fallopia differs from Fagopyrum in a number of characters given by Holub ( 1970).
To this can be added the absence of distinct nectaries and the presence of a
main dendricular vein in each tepal of Fallopia.
Holub ( 1970) divided Fallopia into two sections, Sarmentosae and Fallopia, on
the basis of the woody habit and many-flowered inflorescence of the former, and
the herbaceous habit and few-flowered inflorescence of the latter.
Haraldson ( 1978) considers three sections under Fallopia: section Pleuropterus,
section Parogonum and section Fallopia, mainly on the different trichome types.
However, we did not see the species she placed in section Parogonum (Fallopia
cilinodis, F. cyanchoides).
We agree with those authors who consider Rrynoutria and Fallopia to be a
single genus, for a number of reasons:
I. Both genera are characterized by the same type of stamens. The filaments are
dorsiventrally flattened to cylindrical and dilated at the base, and are covered
(in many cases) with papillae, which occasionally spread onto the receptacle.
The anthers are all introrse and the stamen number is constantly eight
(Figs 26, 27).
2. Both taxa are characterized by outer keeled tepals, as wings develop behind
the main vascular bundle (Fig. 26).
3. The tepa] vasculature is in both cases of the 'dendricular' type. The
epidermal cells are wholly comparable (Fig. 11).
This conclusion is supported by features of the pollen, flower-shape and
inflorescence (Hedberg, 1946), as well as other characters mentioned above.
Steward ( 1930) used the pubescent filaments of F. baldschuanica and F. aubertii
to separate them from F. multijlorum and other species. The present study shows,
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
346
however, that this distinction is not wholly useful, as trichomes occur in most
species, although they are not always well-developed.
The nomenclature of the genus has been a matter of controversy and has led
to much unnecessary confusion, as the group is clearly defined. Hedberg ( 1946)
opts for Tiniaria as a nomen conservandum against the names Reynoutria and
Bilderdykia, on the premise that Tiniaria is the best known and most widely used
name. However, at the present day other names have as much precedence (e.g.
the use of Bilderdykia and Reynoutria by Tutin, 1964). Holub (1970) mentions
Fallopia as the oldest available name for use for a taxon which includes its type,
and it thus has priority.
We consider the genus Reynoutria to be a section of Fallopia for the reasons
given above. The following treatment of the genus is therefore proposed:
Fallopia Adans. emend. Ronse Decraene.
TYPE SPECIES: Fallopia scandens (L.) Hal u b, Folia Phytotax. Praha, 6: l 71-1 77
(1970).
section Fallopia
section Sarmentosae (1. Grintz.) Holub
section Reyn.outria (Houtt.) Ronse Decraene,
BASIONYM:
co~nb.
et stat. nov.
Reynoutria Houtt., Hand/. Regn. Veg., 8: 639 ( 1777).
Reynoutria japonica Hou tt.
TYPE SPECIEs:
Oxygonum Burch. ex Campd. (1819).
SYNONYM:
Ceratogonum Meissn. (1857), pro parte.
The genus has been described on the basis of its broadly winged, non-prickly
fruits and is confined to Africa. The species with prickly fruits were described by
Meissner (1857) as Ceratogonum, but were later combined in Oxygonum as the
distinction is of lesser taxonomic value.
The morphology of the filaments has been mentioned by previous authors
(Meissner, 1857; Bentham & Hooker, 1880; Gross, 1913b; Vautier, 1949;
Graham, 195 7, 1958). The dilated filament bases, associated with the trichomes
on the inner stamens, are comparable with those in Pteropyrum, Calligonum and
Fallopia. They are apparently inserted on the back of the stamens or laterally on
slightly darker extensions, which are reminiscent of structural nectaries. The
identity of the genus is not in question. Oxygonum differs from other genera
essentially in the fused perianth and receptacle which strongly invests the fruit
(Fig. 8). To this we can add the peculiar red trichomes, mamilla-like epidermal
surface and the elongated anthers. The pollen (also observed) is very similar to
that of Pteropyrum or Fallopia. The tepa! vasculature links the genus with
Pteropyrum and Atraphaxis (see Vautier, 1949). We think that the position of the
genus is clearly situated among these genera.
Pteropyrumjaub. & Spach. (1844).
The identity of this genus is unambiguous, although its posltlOn has been
controversial. A strong relationship with Calligonum was found:
l. Both taxa have the same type of trichomes, which are long with a non-ridged
cuticle at the base of the filaments (Figs 9, 28).
GENERIC LIMITS IN POLYGO.NUM
347
2. The tepal epidermis is comparable, as well as the vasculature.
3. The filaments are not dilated at the base and are filiform, not flattened
(Figs. 9, 28).
Atraphaxis seems to be strongly related as well, for reasons discussed under that
genus. The three genera are more closely related to Polygonum than to any other
taxon. A complete separation as a tribe (Dammer, 1893: Atraphaxidae),
subtribe (Gross, 1913b; Jaretzky, 1925: Atraphaxideae), or subfamily (Roberty
& Vautier, 1964: Calligonoideae) is not recommended. Haraldson (1978)
considers Pteropyrum and Atraphaxis to be most similar to the supposed ancestor of
her Polygoneae.
Atraplr.axis L. ( 1753).
SYNONYMs: Artaphaxis Mill. ( 1754).
Pedalium Adans. ( 1763), non L.
Tephis Raf. ( 183 7), non Adans.
Tragopyrum Bieb. ( 1819).
Tragopyron Bieb. ex Wittst. ( 1852).
This genus was recognized very early, on the basis of its fruits and woody
xeromorphic habit and has been maintained as such. Only Atraphaxis spinosa
(Fig. 30; and perhaps A. seravshanica) showed structures reminiscent of short
trichomes, inserted laterally on the filament base. In other species investigated
no traces were found (Fig. 29). Atraphaxis spinosa has the same type of papillae
covered by a cuticle as those found in Fallopia (Figs 30, 27).
The genus is very close to Polygonum and shares the same subulate filaments
with extending base, tepal epidermis and vasculature. On the other hand, the
presence of papillae at the base of the filaments of A. spinosa links the genus with
Pteropyrum and Calligonum. We believe that Atraphaxis has an intermediate
position between Polygonum and the two other genera.
Calligonum L. 1753
This genus was defined by Linnaeus (1753) and has remained stable since
then. It is well separated from other taxa by the higher number of stamens
(10-18 according to Roberty & Vautier, 1964; 10-11 according to Galle, 1977;
12-17 according to Meissner, 1857; 12-18 according to Bentham & Hooker,
1880 and Dammer, 1893) and the four carpels. We recorded 12-13 stamens in
the three species investigated (Fig. 9).
This high number of stamens is unusual in the Polygonaceae and could only
be explained by dedoublement in the inner and outer whorl. This hypothesis
has been accepted by Gross ( 1913), Jaretzky ( 1925) and Galle ( 1977).
According to Jaretzky the tetramery of the ovary is responsible for an increase in
stamen number. Galle ( 1977) studied the ontogeny of the flower and observed
the development of stamen pairs opposite each tepal. He occasionally found
three stamens opposite the first tepal primordium. Maximally three stamens
could develop against each tepal giving a number of 15-18 (cf. Dammer,
1893). In Calligonum comosum we suspect that the three outer tepals are associated
with three stamens and the two inner with two. Clearly the number of stamens
is not important and variable within the genus, but the high number can easily
348
L.-P. RONSE DECRAENE AND J. R. AKEROYD
be linked with the eight stamens of Palyganum sensu lata. The relationships of
Calliganum are with Atraphaxis and Pterapyrum, although the genus has evolved
into a specialized group. The large number of stamens and lack of dilated
filament bases are unique features. Conversely the vasculature of the tepals is
comparable with Pterapyrum, as well as the same type of trichomes and stamen
morphology.
The three genera share a special type of venation (formation of commissural
veins, see Vautier, 1949), the non-fused petaloid tepals, as well as the same tepa!
epidermis and same anatomy (Haraldson, 1978) and pollen (Hedberg, 1946;
L.-P.R.D. unpublished observations).
Discussion rif the characters used
In this study several characters have been identified for their taxonomic
value, and are useful in improving the present classification that has been based
on traditional characters. Stamen number has been considered by many authors
to have little value in the classification of Polygonum sensu lata (Gross, 1913b;
Galle, 1977), as many species show great variability, even within a single
inflorescence. Indeed, as observed by Trail ( 1896): "No very definite relation
has been traced between the position of a flower on the axis and derivations in
structure"_ Some taxa are extremely variable in the number and position of
parts (e.g. Persica ria lapathifolia, P. maculata, Polygonum aviculare, etc.). On the
other hand, some species or even sections show a remarkable stability in their
odd stamen number (Persicaria amphibia, Polyganum undulatum, Persicaria section
Tovara, Fallopia, Fagopyrum, etc.). It is worth mentioning that anomalous numbers
have a strong appeal to botanists to create new sections or separate groups!
However, the taxa reveal some interest in the increase or decrease of the basic
stamen number. In Polygonum sensu lata, the primitive number is undoubtedly
eight and is generally thought to be derived from a structure with six tepals,
nine stamens and a trimerous ovary, by fusion of two transitional tepals and the
loss of one stamen on the spiral (Jaretzky, 1925; Geitler, 1929; Laubengayer,
1937; Vautier, 1949; Galle, 1977; etc.). Occasionally we have found flowers with
a trimerous structure (e.g. Pteropyrum olivieri, Calligonum tetrapterum, Polygonum
aviculare) .
The process of dedoublement (chorisis or splitting) has been advocated to
derive the outer stamen pairs from a single stamen (Eichler, 1878; Dammer,
1893; Gross, 1913b; Geitler, 1929;Jaretzky, 1928; Galle, 1977; see also Fig. 20).
Some genera show a much higher number (Calligonum: 11-18; Symmeria: more
than 40). Galle ( 1977) derives this by a secondary splitting of primordia (see
under Calligonum). The decrease of stamen number is of special interest in
Polygonum sensu lata. The number of parts can be diminished by two mechanisms:
as part of the pollination syndrome under evolutionary pressure of the
pollinator, or as part of a general reduction trend from trimery to dimery, which
affects only the transitional tepals and stamens opposite the vanished carpel
angle. A clear correlation was found between the reduction of the ovary to two
carpels and the number of stamens involved (e.g. in Atraphaxis spinasa, Oxyria
digyna, Persicaria nodosa, P. senegalensis, Palygonum aviculare, etc.).
Further reductions of the outer or inner stamen whorl cannot be linked with
the decrease in carpel number. This means that the loss of more stamens must
be considered independently from the loss of the transitional stamens. This
GENERIC LIMITS IN POLYGO.NUM
349
process is evident in Persicaria section Persicaria, where a dimerous gynoecium is
always associated with the loss of more inner stamens, their position often being
occupied by nectaries. In some cases this variability can be genetically fixed as
an odd number within a section or species.
On the basis ofreductions in stamen number, we were able to distinguish two
groups. The filament morphology added some further interest to their
distinction.
1. The first group always has inner stamens, which are larger than the outer
and flattened, with a dilated base. The outer stamens are often reduced in size
or absent. Typical examples can be observed in Polygonum, Oxygonum, Fallopia,
Atraphaxis and Polygonella (Figs 7, 8, 23).
2. The second group has filiform to flattened, elongated stamens which are not
dilated at the base. The inner whorl is little differentiated from the outer,
although it is longer. Reductions mostly occur in the inner whorl. This type is
found in Persicaria, Fagopyrum, Harpagocarpus and Koenigia (Figs 1, 2, 4, 6, 18, 19).
It is concluded that nectaries are of considerable taxonomic importance in the
Polygonaceae. It has been shown that the presence of nectaries is correlated
with the occurrence of papillae or trichomes on the back or on the receptacle
behind the mamillae. This feature will be discussed in a further publication
(Ronse Decraene & E. Smets, in preparation). The character divides Polygonum
sensu lato and related genera into three distinct groups of taxa:
1. The nectaries are present as receptacular mamillae behind the stamens or
between them (Figs 12, 14, 3, 1). They are free or confluent into a disc-like
structure (Figs 19, 20, 18). In other cases they fuse with the stamen bases
(Fig. 15). Papillae are associated with these nectaries, inserted in a fold on the
back, or on the receptacle (e.g. Persicaria, Koenigia, Fagopyrum, Harpagocarpus;
Figs 12, 14, 21).
2. Clearly differentiated nectaries are absent. Papillae or trichomes may occur
at the base of the filaments or spread onto the stamens and receptacle (e.g.
Atraphaxis, Calligonum, Fallopia, Pteropyrum, Oxygonum; Figs 9, 8, 27, 28, 30, 26).
3. Nectaries are absent or not visible as independent structures, but the filament
bases are inflated. No papillae or trichomes are found (e.g. Polygonum,
Polygonella; Figs 7, 23).
The inner stamens are always linked with two lateral nectaries in Persicaria,
Harpagocarpus, Koenigia and Fagopyrum. They may be distinct as in Fagopyrum,
Persicaria section Persicaria and section Tovara, or the inner may fuse with the
inner filaments as in Persicaria sect. Bistorta (Figs I, 3, 4, 15). In section
Aconogonon and Koenigia all nectaries may fuse into a continuous disc (Figs 18,
19, 20, 21 ).
The tepals are mostly five in number, but they are occasionally fused or are
reduced (Persicaria hydropiper, Koenigia nummularifolia, Polygonum aviculare, etc.).
Fusion of the tepals probably leads to the higher insertion of the stamens
(Persicaria section Persicaria). In sections Aconogonon and Koenigia the outer
stamens are not displaced but fuse abaxially with the tepals. In Fagopyrum
practically no fusion occurs. The same happens in Pteropyrum, Atraphaxis and
Calligonum, although slight abaxial fusion may occur. Polygonum, Fallopia,
Polygonella and Oxygonum also show a degree of tepal fusion, without
350
L.-P. RONSE DECRAENE AND]. R. AKEROYD
displacement of stamens. In Koenigia the outer tepal whorl often becomes
strongly reduced in size or may disappear (K. islandica, K. delicatula). In section
Aconogonon of Persicaria the outer whorl is often smaller than the inner.
Pteropyrum, Calligonum and Atraphaxis have a petaloid showy perianth, but the
outer whorl is much smaller. A clear differentiation of the outer and inner whorl
occurs in Polygonum, Polygonella and Fallopia, where the outer tepals are angular
or keeled (Figs 7, 26).
Based on tepal vasculature, three groups could be defined:
I. Taxa with a trifid venation (Fig. 10), as in Persicaria, Koenigia and Fagopyrum
(with some exceptions). This probably represents the primitive type in the
Polygoneae. In Persicaria section Persicaria secondary ramifications are rare and
short (Fig. l). In section Aconogonon much branching occurs, giving a number of
long parallel veins (Fig. 2). In Koenigia venation is reduced, sometimes to a
single short vein (Fig. 5).
2. Taxa with a dendricular venation (Figs 7, II), as in Polygonum, Fallopia and
Polygonella. The two laterals are in most cases reduced or rarely weakly
developed (e.g. Polygonum afromontanum). The main vein gives off a variable
number of secondary veins. In some cases branching is sparse (e.g. Polygonum
douglasii) or does not occur at all (e.g. Polygonella species).
3. Taxa with commissural and anastomosing venation, as in Atraphaxis, Pteropyrum,
Oxygonum and Calligonum. All possess commissural veins between the inner and
outer tepals; laterals are long and abundant. Atraphaxis shows a dendricular
venation (as in 2.), with anastomosing laterals (see Vautier, 1949). The three
other genera produce branching laterals in a trifid pattern.
The tepal epidermis provides further evidence for the distinctions made
between different taxa. On the whole, two main groups could be differentiated:
I. The first mostly has rectangular to elongated cells. The anticlinal walls are
straight or undulating. The cuticle is smooth or striate. A reticulate pattern is
absent and individual cells do not differ much from each other (Figs 13, 17).
This type occurs in Koenigia, Persicaria, Harpagocarpus and Fagopyrum.
2. The second has irregular to elongated cells (rarely rectangular). The
anticlinal walls are mostly sinuate. The cuticle rarely shows a longitudinal
striation, but has strong orthogonal to reticulate ridges or striae, often without
correlation between cells. The individual cells vary much in size and shape
(Figs 24, 25). This type occurs in Polygonum, Polygonella, Atraphaxis, Fallopia,
Pteropyrum, Oxygonum and Calligonum. Fagopyrum esculentum and the species of
Oxygonum have a unique cell structure. The epidermis is covered with mamillae
or scales with a striate cuticle. However, both types could be linked to one of the
cell types. Within the sections and genera some importance can be attached to a
particular type of epidermal cell.
CONCLUSIONS
A revised taxonomy of Polygonum sensu lato is given in Appendix 3.
We are unable to restrict the species studied to one tribe Polygoneae for
several reasons, discussed above. Within Polygonum sensu lato a clearcut division
has been made, leading to the recognition of two distinct lines of evolution:
Firstly, the Polygoneae includes the following genera: Polygonum, Polygonella,
GENERIC LIMITS IN POLYGO.NUM
351
Fallopia, Oxygonum, Pteropyrum, Calligonum, Atraphaxis (see Appendix 3). They
have the following features in common:
1. The filaments (especially the inner) are often dilated at their base and mostly
broadly flattened (Figs 7, 23, 27, 29).
2. If nectaries are present these never occur as outgrowths of the receptacle.
Trichomes or papillae may be present at the base or lower half of the filaments.
The receptacle may have a glandular zone of tissue (Figs 27, 30, 28, 31, 26, 9).
3. The vasculature of the tepals consists mostly of a single branching
dendricular vein (Figs 7, ll). However, another type occurs in Oxygonum,
Pteropyrum, Calligonum and Atraphaxis.
4. The outer tepals are often angular, clearly differentiated or keeled (Fig. 26).
5. If reductions occur, these always affect the outer stamens (except for
occasional reductions of the flower to dimery).
6. The tepal epidermis is strongly papillose, never smooth and has irregular to
elongated cells (Figs 24, 25).
O~gonum is probably a relatively primitive relative of Polygonum, but
represents a distinct, geographically restricted line. Atraphaxis represents the link
between Polygonum or Fallopia, and Calligonum or Pteropyrum, sharing characters of
both groups.
Polygonella is to be considered as an extreme line of evolution of Polygonum,
restricted to North America.
Secondly, the Persicarieae consists of the following genera: Persicaria,
Fagopyrum, Harpagocarpus and Koenigia. These taxa are characterized by a
number of features not shared by the Polygoneae:
l. The filaments are not dilated and dorsiventrally flattened, but are mostly
slender, cylindrical to slightly flattened (Figs l, 2, 18, 19).
2. Nectaries are present and are always visible as distinct outgrowths of the
receptacle (nectaria persistentia c( Smets, 1986). Papillae are mostly present
and occur in relation to the nectaries (Figs 12, 14, 18, 19, 21).
3. The vasculature of the tepals is of the trifid type (three main veins, which can
further branch (Figs 1, 2, 3, 5, 10).
4. The outer tepa1s do not differ from the inner, except in size and are not
angular or keeled (Figs 1, 2, 4, 5, 6).
5. If reductions occur, these affect the inner and transitional stamens and outer
tepals.
6. The tepal epidermis consists of rectangular to elongated cells with a smooth
or usually longitudinally striate cuticle (Figs 13, 17).
Fagopyrum probably represents a putative 'primitive type' to which Persicaria
and Koenigia are linked.
The distinction between the two tribes is supported by evidence from different
disciplines (see discussion above) and partly agrees with Haraldson's ( 1978: 65)
proposal of a recognition of the Persicarieae and Polygoneae, except for her
placing of Fallopia (excluding Rrynoutria) and Harpagocarpus in her Coccolobeae,
and of Fagopyrum in Polygoneae: a point of view that we are unable to support.
Revision of taxa should be extended to other groups in the Polygonaceae, as
the relationships ramify much further, but such a proposal goes beyond the
scope of this study.
A key is given to clarify the relationships of taxa discussed above (see
Appendix 3).
352
L.-P. RONSE DECRAENE AND j. R. AKEROYD
ACKNOWLEDGEMENTS
The present study was carried out at the Plant Science Laboratories,
University of Reading, in part fulfilment by L.-P.R.D. of the M.Sc. degree in
Pure and Applied Plant Taxonomy.
We are most grateful to Dr J. R. Barnett and the staff of the SEM and
Photography Units for their kind and valuable help in the execution of the
practical work. Sincere thanks go to Dr A. P. Conolly for helpful discussion and
for providing literature, and to J. P. Bailey for providing information,
photographs and preserved material. Thanks also go to E. Smets for critical
reading of the text and valuable comment on the nectaries, and to Prof. Dr E.
Petit for his comments.
We are much obliged to the curators of the herbaria at Kew (K) and
Reading (RNG) for putting specimens at our disposal, and to the Botanic
Gardens mentioned in the text for providing living material.
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L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
354
APPENDIX 1
Results
The species are listed in the tables with some of the characters observed. All species of Polygonum sensu lato are
listed as Polygonum L. in order to avoid confusion that may arise by the use of segregate genera. The
provenance of the material is listed in Appendix 2. For t·onvcnicm·c each character will be assigned a number
as follows:
2
POLYGONUM L.
Section Persicaria
P. persicaria L.
Trifid
Ovate, fused for
1/3
P. nodosum Pers.
Trifid-bifid
Ovate, fused for
1/3
P. pennsylvanicum L.
Trifid-bifid
(inner)
Erect, ovate,
fused for 1/2
P. minus Huds.
Trifid
P. hydropiper L.
Trifid
P. amphibium L.
Trifid
Outer, smaller,
ovate
Almost
completely
fused, ovate
Fused for 1/3,
ovate
P. barbatum L.
Trifid
P. virginianum L.
Trifid
P. ne'!Jiliforme Nakai•
Trifid
Section Cephalophilon
P. capitatum Ham. Buch.
3
5
Rectangular
Straight
Rectangular
Undulating
Few, shorter
Rectangular
Undulating
Few, erect
Long,
rectangular
Rectangular,
short
Straight
Slightly
undulating
Few, at different
levels, short
Rectangular
Sinuate
Fused for 1/2
Few, short
Rectangular
Straight
Fused for 1/3,
obtuse to acute,
O±smaller
Outer smaller,
fused for 1/2,
acute
Few, long
Rectangular
Straight
Few, long,
arising at same
height
Rectangular
Sinuate
Trifid
Fused for 1/2,
ovate
Few, long at
same level
Rectangular
Straight
P. runcinatum Buch.Ham.
Trifid
Not observed
Abundant
Rectangular to
elongated
Straight
P. glaciate (Meissn.)
Hook.
Trifid
Long-erect
Few, long, erect,
at different
levels
Rectangular
Straight
P. chinense L.
Trifid
Large, about
same size, fused
for 1/3
Not observed
Rectangular
Straight to
sinuate
Section Amblygonon
P. limbatum Meissn.
Trifid
Inner larger,
fused for 1/3
Abundant,
shorter
Rectangular
Undulating,
straight
Trifid, curving
tops
Obtuse apex,
fused for 1/3
Few, shorter
Not observed
Not observed
P. senegalense Meissn.
Not observed
4
Few, at different
levels, short
GENERIC LIMITS IN POLYGO.NUM
355
I = Tepa! venation type; 2 = External tepa! morphology; 3 = Secondary ramifications of the main vl'ins;
4 = Tepa! epidermis; cell shape; 5 = Anticlinal walls of epidermal cells; 6 = Cuticle; 7 "' Floral formula;
8 = Filament morphology; 9 =Stamen insertion; 10 = Nectaries; II = Papillae or trichomes; I = Inner,
T =transitional, 0 =outer (see introduction), A= stamen, P =tepa!, G =carpel.
Floral formula gives the frequent variation in numbers, unless indicated. Voucher specimens of the personal
collections are kept at the University of Leuven, Belgium (LV).
Footnotes are given at the end of this Appendix.
6
Smooth, light
longitudinal
striae
Smooth
Smooth
Longitudinal
striae
Longitudinal
striae
Irregular to
longitudinal
Longitudinal
striae
Irregular to
straight striae
Longitudinal
discontinuous
striae
7
P5A6-8G2-3, T
A sometimes
missing
P4-5A6-8G2, I
TA&IIA
missing
P5A6-7G2 I, I
TA& I I A
missing
P4A5-6G2, 2 T
& I I A missing
P4-5A5G2, 3 I A
absent (constant
feature)
P5A5G2, 3 I A
missing
(constant
feature)
P5A8G3
P4A5G2, I T P,
IIA&2TA
missing
P4A5G2, I T P,
IIA&2TA
missing
8
Outer larger,
inner filiform,
stout
4 outer larger,
inner small,
filiform
Outer about
same length as
inner, filiform
Inner slightly
longer
Filiform
10
9
Outer higher on
fused tepals
Outer inserted
higher
Outer inserted
higher
4 outer inserted
higher
5 outer on fused
tepals
Free, large
globular
mamillae
Free,
inconspicuous
Free, I
occasionally
replacing I A
Free, replacing
inner stamen
Free, replacing
inner stamens
II
Short papillae
bt>hind nectaries
Not observed
Not observed
Not observed
Not observed
Flattened,
filiform
5 outer fused
with nectaries
Fused into a
ring, rt>placing I
stamens
Not obst>rved
Outer smaller,
filiform to
flattened
Flattened, I
slightly longer
than outer
About same
length, flattened
and broad
Outer inserted
higher
Small, globular
Few, cylindrical
papillae in fold
behind nectary
Outer inserted
slightly higher
Obtuse, large
replacing I A, 0
smaller, free
Free, acute,
replacing inner
stamen
Outer clearly
higher
Free, in ring
cylindrical, some
replacing
stamens
Fused into high,
flat rim with
stamen bases
Globular,
inserted on out·
growth of
receptacle
Almost fused
into spongy disc
Not observed
Short, numerous
in fold of
nectaries
Smooth, undeep
striae
P5A6-8G3, I I
A& ITA
missing
Cylindrical to
flattened
Outer higher,
reaching same
height
Smooth undeep
striae
P5A?G3
Weakly
longitudinally to
obliquely striate
P5A8G3
Outer shorter,
cylindrical to
flattened
Very long,
2 x length of
pistils, flattened
Outer higher,
reaching as high
as I
Outer slightly
higher
Deep
longitudinal
striae
P5A8G3
Flattened to
triangular, long
Outer higher,
curved; inner
straight
Deep
longitudinal
striae
Not observed
P5A7G2, IT A
missing
Inner longer
flattened-filiform
Outer inserted
higher
Conspicuous,
free and ovate
Short papillae
on receptacle
P4-5A4-7G2,
ITA&IA
tendency to
reduce
Filiform,
flattened, shorter
than tepals
Outer inserted
higher, shorter
Free,
Not observed
inconspicuous,
replacing T A.
Not observed
Not observed
Large, lying
behind nectaries,
club-like
L.-P. RONSE DECRAENE AND J. R. AKEROYD
356
Appendix I Continued
3
2
5
4
POLYGO.NUM L.
P. lomentosum Willd.
Trifid
Outer smaller,
ovate
Abundant,
shorter
Not observed
Not observed
P. orientale L.
Trifid
Large, fused for
2/3
Abundant,
shorter
Rectangular
Sinuate to
straight
Section Echinocaulon
P. peifoliatum L.
Trifid
Fused for 1/2,
obtuse apex
Few, short to
long
Rectangular
Straight
P. sieboldii Meissn. b
Trifid
Fused for 2/3,
erect
Few, long, at
different levels
Rectangular
Straight
P. strigosum R. Br.
Trifid
Fused for 2/3,
ovate
Few, short
Rectangular
Weakly sinuate
P. pendunculare Wall. ex
Meissn.
Trifid
Fused for 2/3,
obtuse apex
Very few to
none
Rectangular
Straight
Section Aconogonon
P. sericeum Pall.
Not observed
Fused for 1/3
Few
Rectangular
Straight
P. hookeri Meissn.
Trifid
Not observed
Not observed
Not observed
*P. polystachyum Wall.
ex Meissn.
Trifid
Large, ovate
with obtuse apex
Few laterals of
same length
Shortly
rectangular to
elliptical
Weakly sinuate
*P. campanulatum Hook.
F.
Trifid
Ovate, fused for
1/2, largt•
Long laterals
diverging at
base
Rectangular
Weakly sinuate
P. paw/owskyanum Glehn
Trifid
Fused for 1/3,
obtuse
Few
Rectangular
Weakly sinuate
P. divaricatum L.
Trifid
Outer smaller
than inner
Occasional long
on different
heights
Rectangular
Straight
*P. weyrichii F. Schmidt
ex Maxim.'"
Trifid
Rectangular
Straight
P. angustifolium Pall. d
Trifid
Outer smaller
with acute to
obtuse tips,
fused at base
Broadly ovate
outer smaller
Occasional to
often
branching, long
Rectangular to
elliptical
Straight
Section Bistorta
P. bistorta L.
Trifid
Few, abundant
long
Rectangular
Weakly sinuate
Fused for 1/3,
obtuse, outer
slightly narrower
GENERIC LIMITS IN POLYGO.NUM
6
7
8
9
357
10
II
Not observed
P5A7G2, IT A
missing
Elongated and
flattened
Outer inserted
higher, shorter
Longitudinal
striae
P5A7G2, IT A
missing
(constant
featurt')
Flattened, as
long as tepals
Outer inserted
little higher
Smooth, weakly
striate
PSA8G3
Irregular
longitudinal
striae
PSA7?G3
Outer about
same length as
inner
Filiform, inner
longer
Outer inserted
higher at tepal
divergence.
Outer inserted
higher on fused
tepa Is
Smooth
PS A7?G3
Outer inserted
higher
Smooth
P4A5G2, 3 I A
missing
(constant
feature)
Outer half as
long as inner,
filiform to
flattened
Slender,
flattened
Outer inserted
higher
Inconspicuous
Not observed
Practically
smooth
P5A8G3
Outer inserted
behind inner
P5A7G3, IT A
Occ. missing
Inserted at
about same
height
Outer slightly
higher, fused
with tepals
Weak disc, fused
with filament
bases
8, (·onspicuous
red globular,
confluent
Strong, fused
with filament
into disc; us. 8
Not observed
Not observed
Smooth, inner
slightly longer
rather flat
Filiform, small
Outer curved,
fused for 2/3
with tepals
Flat disc,
confluent with
stamen bases
Short, spreading
on receptacle
Outer inserted
higher where
tepals free
Outer little
higher, reaching
as high as I
8, globular &
tuberculate;
fused into ring
Pink, globular,
fused into disc
Not observed
Outer recurved,
inserted higher
Small, confluent
Not observed
Longitudinal
striae
P5A(6~7)8
G3-4
Occ. T A
missing
Filiform to
cylindrical,
about same
length
Cylindrical,
smooth, inner
erect, of same
length
Slightly
flattened,
elongated
Slender,
flattened; outer
anther length
shorter than I
Filiform to
flattened, about
same
Circular,
conspicuous I
replacing T
stamen
7, free, a large
replacing T A.
Rectangular
Small,
inconspicuous
Stalklike,
rectangular,
fused into cont.
rim
Elliptic,
inconspicuous
Densely covering
the receptacle
Numerous
behind nectaries,
cylindrical,
smooth
Large, obtuse,
cylindrical,
spreading
Not observed
Not observed
Not observed
Numerous,
cylindrical in
ridge beh. nect.
Deeply ridged,
longitudinal
PSA8G3
Smooth
PSA8G3
Smooth or
weakly
longitudinal
PSA8G3
Smooth to
slightly
longitudinal
P(4)5A(7)8 G3
Occ. I A missing
Smooth or
slightly
longitudinal
P(4) 5A(7) 8G3
Occ. I A missing
Cylindrical and
broadly filiform
Inner erect,
outer curved
behind disc
Fused into
flattened disc,
conspicuous
mamillae
Numerous to
few, in fold
behind nectaries,
cylindrical
Short
longitudinal
striae
PSA8G3
Flattened, often
one side of
flower reduced
or A of different
length
Outer inserted
slightly higher
Brown mamillae,
I fused with I A,
0 free, small
Few in fold,
cylindrical
I
Cylindrical, in:·
fold behind
nectaries
L.-P. RONSE DECRAENE AND J. R. AKEROYD
358
Appendix I Continued
2
3
4
5
POLrGO.NUM L.
P. viviparum L.
Trifid
Mostly free,
slender
Sparse, short
Rectangular
Undulating
P. affine D. Don
Trifid
Slightly fused at
base
Few
Elongated to
rectangular
Undulating
P. vaciniifolium Wall.
Trifid, 1 tepals
with I vein
Erect &
elongated, fused
at base
Few
Elongated to
rectangular
Straight
P. amplexicaule D. Don
Trifid
Free for 3/4
elongated and
erect
Few
Elongated to
rectangular
Sinuate
Dendricularly
branching main
vein
Outer slightly
angular, inner
larger
Few short
Elongated to
irregular
Undulating
Dendricularly
branching main
vein
I main vein
Outer slightly
angular
elongated
Outer more
obtuse, inner
enlarging in
upper half
Large, inner
broader
Few
Irregular and
elongated
Undulating
Few, alternating
Irregular and
elongated
Undulating
Numerous
branching erect
to descending
Regular,
dendricular,
numerous
Irregular
Undulating
Irregularly
elongated to
rectangular
Undulating to
straight
Few to none
Irregular to
elongated
Undulating
Regular,
descending
Elongated to
irregular
Undulating to
straight
All with acute
apex, ± fused at
base
Practically none
Rectangular to
elongated
Undulating
main vein
Outer with
angular midrib,
acute
Few short
Ia terals in 3
outer
Strongly
irregular
Strongly
undulating
P. molliaeforme Boiss.
I main vein
Outer slightly
angular &
acute; inner
more expanded
& obtuse
Rectangular to
irregular
Undulating
Section Tephi.<
P. afromontanum
Greenway
I main vein to
trifid
Outer slightly
keeled & acute,
inner larger
Elongated to
rectangular
Undulating
Section Po(ygonum
P. aviculare L.
P. scoparium Req. ex
Loisel
P. jlorihundum Schlecht
ex Sprengel
P. oxyspermum C. A.
Meyer & Bunge ex
Ledeb.
P. patulum Bieb.
I main vein
P. plebejum R. Br.
I main vein
P. maritimum L.
P. californicum Meissn.
P. douglasii E. Greene•
I main vein
main vein
I main vein
Same size, outer
not angular,
fused in lower
half
3 outer more
angular than
inner, with
rugose surface
All similar,
ovate, obtuse
Short, well
developed
laterals
GENERIC LIMITS IN POLrGONUM
7
6
Longitudinal
sinuate striae
PSA8G3
Longitudinal
sinuate striae
PSA8G3, occ.
with 2 0 A
fused or I
staminode
PSA8G3
Longitudinal
sinuate striae
Undulating
longitudinal
striae
PSA8G3
Short reticulate
ridges
P4-5(6)A6-8G23 variable
Short reticulate
ridges
PS-6A6-8G3
0 A occ.
staminodial
PSA8G3
Random &
short ridges
Deep random
ridges
PSA8G3
Random surface
striae
P4-SA8G3
Irregularly
striate
P4-6A6-8G3
tendency to
variability
Finely striate &
at random
PSA8G3
Striate
orthogonal to
long axis
PSA8G3
Deeply
irregularly
ridged
P5A8G3
Striae irregular
PSA4-SG2, 0 A
not dedouble
Irregular to
longitudinal
PSA6G3, 0 A
not dedouble
8
9
Broadly
cylindrical, outer
slightly smaller
Cylindrical to
flattened
Long & equal,
exserted above
tepals
Equally long, 0
inserted behind
disc
Long & slender
slightly
flattened, I
longer
Cylindrical, I
fused with I
nectaries, long
All erect, outer
little higher
Erect I, 0 more
curved behind
0 nectaries
I with flattened
I always present,
filaments,
0 often not
dilated at base,
dedouble, ±as
outer smaller &
high as inner
filiform
I larger with
0 fused for short
swollen filament distance with T,
base
±higher
Outer little
Enlarged,
flattened; inner
higher, behind
larger with
inner
swollen base
0 behind I,
Flattened &
bottle shaped, I
flanking main
vein of 0 tepals
larger than 0
Flattened, I
Outer inserted
larger, becoming behind inner
progressively
smaller
Dilated & short
0 behind I
with
fused abax. with
quadrangular
tepals
bases
Inner longer
Inserted in ring
than outer, all
around ovary
with dilated
base
Filaments
Outer inserted
broadening tow. higher & behind
base, elongated
inner
& acute, 0
shorter
Inner regularly
Outer inserted
broadening tow.
jligher & behind
base, flattened
'inner
0 shorter
Inner larger
Outer inserted
with subulate
higher, somefilaments, all
times I pair
dilated at base
missing
Inner longer,
progressively
reducing in size,
all dilated
Outer inserted
higher
359
10
Inner completely
fused with I A
0 reduced
I fused with I
stamens into
disc, conspicuous
0
I stamens with
inconspicuous
mamillae, 0
almost absent
0 globular &
consp., I fused
with I stamens
II
Not observed
In ridge of nect.
back, few
cylindr.
Very lew in
ridge of nect.
back
Few in ridge of
0 nect. back
L.-P. RONSE DECRAENE ANDJ. R. AKEROYD
360
Appendix I Continued
2
POLrGO.NUM L.
Section Tiniaria
P. .rcandens L. 1
5
4
3
main vein
Outer broadly
winged or keeled
Laterals
upwards,
candelabra-like
Irregular to
elongated
±
P. convolvulus L.
I Main vein
Narrowly keeled
or angular
Few laterals
upwards
Straight
P. aubertii L. Henry
I Main vein
Outer with welldeveloped crest
Regular erect
Elongated,
irregular, more
rectangular to
veins
Irregular to
rectangular
P. baldschuanicum Regel
I Main vein
Strongly winged
outer tepals
Regular,
candelabra-like
3ry branching
Irregular to
rectangular
Undulating
P. pterocarpum Wall. ex
I Main vein
Outer strongly
winged
Practically none
Irregular to
rectangular
Undulating
I Main vein
3 Outer keeled
to hooked,
enclosing inner
Occasionally,
short
Irregular
Undulating
I Main vein
3 Outer keeled,
enclosing 2
inner, ovate
Few,
progressively
reduced to I
tepals
Irregular to
rectangular
Straight
Single, short
Short & ovate,
fused for 1/3
Rectangular to
elongated
Slightly
undulating
0: single vein 1:
trifid
Fused at base, 2
outer reduced
Rectangular
Undulating
K. pilosa Maxim.
0: single vein 1:
trifid
Rectangular
Undulating
K. nummularifo/ia
Trifid
Fused at base, 0
occasionally
reduced
Fused at base,
occasionally I
completely fused
with 0
Large, fused at
base, extending
above middle
Rectangular
Undulating
Rectangular to
elongated
Undulating to
straight
Meissn. in Wall.
*P. sachalinense F.
Schmidt ex Maxim.
*P. cuspidatum Sieb.
&
Zucc. 1
KOE.'.N/G/A L.
K. islandica L.
K. delicatula (Meissn.)
Hara
(Meissn.) Mesicek &
Sojak
K. forrestii (Diels)
Trifid
Hedb.
K.jilicaulis (Wall. ex
Meissn.) Hedb.
OXrGO.NUM Burch.
0. dregeanum Meissn.
0. de/agoense Kuntze
Straight
Straight to
irregular
Not observed
Fused at base to
1/3, ovate
Not observed
Rectangular to
elongated
Slightly
undulating
I Main vein,
numerous
laterals
Ovate,
elongated, fused
around ovary for
1/2
Ovate,
elongated, fused
for 1/3 with
receptacle
Abundant,
irregular &
anastomosing
Rectangular to
broadly
irregular
(mamillae)
Irregular &
mamilla-like
Irregular
I Main vein,
numerous
laterals
Several long,
anastomosing
Irregular
GENERIC LIMITS IN POLYGO.NUM
7
6
Irregular
reticulate ridges
P5A8G3
Fine irregular to
longitudinal
striae
P5A8G3
Longitudinal to
straight striae
P5A8G3
Long striae at
random
P5A8G3
Longitudinal
random striae
not correlated
between cells
Rough with long
random striae
P5A8G3
P5A8G3
Mostly
longitudinal
random striae
P5A8G3
Longitudinal
striae
P3(4)A3G3
prob. 3 0 P and
3 0 A present
Deep
longitudinal
striae
Deep
longitudinal
striae
Longitudinal
striae
P5A8G3
8
9
Flattened,
progressively
broadened
towards base
Flattened,
slightly
broadening
towards base
Slender, with
broadening base,
cylindrical
Slender &
symmetrical,
dorsi ventrally
flattened
Outer ( 1.8~2.0
mm) inserted
higher than I
(2.0~2.5 mm)
Outer inserted
higher & shorter
Flattened, about
the same length
All inserted at
about the same
height on
extension
Outer inserted
little higher
Long, filiform
flattening
towards base,
±same length
I larger,
widening at base
(only female
flowers seen)
361
10
II
Numerous,
short, in lower
filament half
Short, on I
stamen bases
extending on
receptacle
Numerous, on
sides & back of
filaments
Numerous in
lower half of
Inner longer
than outer,
almost in I ring
Inner longer
than outer,
almost in I ring
stamen,
spreading on
recept.
Long &
numerous on
recept. & stamen
base
Occ. on base of
filament or
absent
Outer inserted
little higher
Short,
unicellular in
lower filament
parts
P3-5A5G2, 2 T
A missing
Slightly
flattened &
short, fused for
I /2 to tepa Is
Flattened, short,
outer
staminodial
Flattened &
smooth
Outer inserted
higher than
straight inner
Outer inserted
higher
P5A5G2, 3 I A
missing
Flattened &
short
Inserted at same
height
Densely packed
longitudinal
striae
P5A8G3
Flattened to
cylindrical, stout
I upright, 0
curved, inserted
behind disc
Straight
longitudinal
striae
P4-5A3-6G?, T
and I A occ.
missing
Flattened to
cylindrical, short
Outer inserted
higher
Random to
longitudinal
tightly pressed
striae
Randomly
ridged
P5A8G3
Inner longer,
cylindrical to
flattened, with
expanded base
Inner larger,
with expanded
base, flattened
Fused with tepa[
tube, 0 little
higher
Tufts of long red
hairs, lateral on
filament
Shorter than
tepals, I fused
into ring around
G
Red tufts
laterally &
abaxially on
stamens base
P5A8G3
Apparently on
rim surrounding
ovary
Low rim
flanking inner
stamens
Low rim
flanking inner
stamens
Low flattened
rim flanking I
stamens
Low number,
stalked & dublike
Low number
dub-like
Thickened
continuous disc
fused around I
stamens
Shallow disc
fused with inner
stamen bases
Numerous in
large fields
behind nect.
Numerous clublike, behind
nectaries
Short, globular,
few to numerous
L.-P. RONSE DECRAENE AND J. R. AKEROYD
362
Appendix I Continued
3
2
OXYGO.NUM Burch.
0. alatum Burch.
main vein,
many laterals
FAGOPYRUM Mill.
F. esculentum Moench.
Trifid
Fused in lower
1/2
Almost free
ovate, oblong
Several
anastomosing,
shorter
Mamillae
Numerous, erect
Dorsiventrally
exserted scales
& anastomosing,
5
4
Irregular
shorter
F. dibotrys (D. Don)
Hara
Not observed
Free
Not observed
Rectangular
short
Straight to
undulating
F. leptopodum (Diels)
Hedb.
Irregularly
branching main
vein
Obtuse,
petaloid, free for
more than 2/3
Abundant,
short, at
different levels
Rectangular
Undulating
F. giraldii (Damm. &
Diels) Haralds.
Trifid
Broad and
petaloid, ovate
Abundant,
short, at
different levels
Rectangular
Undulating
HARPAGOCARPUS
Hutch. & Dandy
H. snowdenii Hutch. &
Dandy
Dendricular to
trifid
Fused for 1/3
Short, abundant
laterals
Rectangular
Undulating to
straight
POLYGONELLA
Michx
P. parksii Cory
One main vein
About same size,
ovate, narrowing
at base
Irregular
Undulating
P. polygama (Vent.)
Engelman & Gray
One main vein
Inner larger,
spreading in
upper half, outer
± angular
Irregular to
elongated
Undulating
P. parviftora Michx.•
One strong main
vein
Elongated
Undulating
P. articulata (L.) Meissn.
One main vein
Outer smaller &
slightly keeled,
inner broad
About same
length,
narrowing at
base
Irregular to
rectangular
Straight to
strongly
undulating
P. americana (Fisch &
Mey). Small
One main vein
Outer reflexed,
smaller than
inner, which
extend in upper
half
Rectangular
Straight
main
dendricular vein
3 inner larger,
erect in fruit,
outer angular
Few,
anastomosing,
short
Irregular to
polygonal
Straight
main
dendricular vein
Free to base,
inner larger,
broad, outer
angular
Not observed
Irregularly
elongated to
rectangular
Straight
PTEROPYRUM jaub
& Spach
P. olivieri Jaub & Spach
P. scopariumjaub &
Spach
GENERIC LIMITS IN POLYGO.NUM
7
6
8
9
363
10
II
Red, associated
with inner
stamen bases
Randomly
ridged
P5A8G3
Flattened, inner
slightly longer
Inner on
extension of
receptacle, 0
behind
Longitudinal to
undulating striae
P5A8G3
Outer inserted
little higher
Clearly inserted
behind I A,
globose
Numerous,
smooth,
cylindrical,
behind ncct.
Thick
longitudinal
striae
Undulating to
longitudinal
striae
P5A8G3
Outer inserted
little higher
Stalked &
globose, behind
I stamens
Globular, on
same height
Not observed
Short,
longitudinal
ridges
P5A8G3
Cylindrical,
flattened with
flap-like
appendages,
outer shorter
Flattened, inner
larger & longer
than outer
Inner longer,
flattened with
flap-like
appendages
Flattened, long
with conspicuous
flap-like
appendages
Longitudinal
striae
P5A8G3
Deep reticulate
ridges
P5A8G3
Deep reticulate
ridges
PSA8G3
Deep reticulate
ridges
P5A8G3
Deep reticulate
ridges
P5A7-8G3, I 0?
A occ. missing
Random to
orthogonal striae
P5A8G3
Strongly ridged,
random striae
P5A8-9G3, occ.
both 0 A
developed
Deep,
longitudinal or
sinuate striae
P5A8G3
P5A8G3
Outer inserted
higher where
tepals s!'parate
Numerous,
smooth,
cylindrical
Outer inserted
higher behind
nect.
Free, globular,
behind inner
stamens
Not observed
Cylindrical,
short, inner
slightly longer
with lateral flap
Outer inserted
little higher
Well-developed
and globular
mamillae
Not observed
Flattened, I
larger with
protruding &
extended
filament base
Flattened, I
larger, all
abruptly
widening tow.
base
Flattened, I ±
longer, strongly
widening at base
Flattened, I
abruptly
widening at
base, 0 ±
extended
Flattened, 3 I
widening
abruptly in
lower half, 0
only ± widened
Fused into a
ring around
ovary
Filiform, not
larger at base; I
not differing
from 0
Filiform, with
slightly
expanded base
Outer inserted
slightly higher
Outer inserted
little higher
All connate into
a short tube
forming a
conspic. rim
0 A inserted
behind larger
lA
Outer slightly
higher, adnatc
on receptacle
Few, long tufts
at base of
filaments
Outer slightly
higher, adnate
on receptacle
Long tufts at
base of filaments
364
L.-P. RONSE DECRAENE AND J. R. AKEROYD
Appendix I Continued
2
P1EROPYRUM Jaub.
1'. aucheri Jaub. &
Spach
ATRAPHAX/S L.
A. huxifolia Jaub. &
Spach
I with I vein, 0
with long
laterals
3
4
5
Inner larger,
broad
Abundant
anastomosing
and erect
2 Outer smaller,
3 inner broadly
ovate
Elongated and
irregular to
rectangular
Undulating to
straight
Irregular to
elongated
Irregular
A. spinosa L.
Strongly
developed main
vem
2 outer smaller,
enveloping
larger inner
Abundant
anastomosing
lateral
ramifications
Numerous long,
branching
anastomosing
A. hillardieri Jaub. &
Spach
I main vein
2 Outer smaller,
angular, 3 inner
broadly ovate
Extensively
branching long
veins
Elongated &
irregular
Undulating
A. seravshanica Pavl.
main vein
Outer narrow,
inner broad &
large
Abundant, small
lateral
ramifications
Irregular to
rectangular
Undulating
main vein with
long & large
laterals
Outer smaller
than inner,
ovate
Numerous few
& parallel,
anastomosing
Irregular to
elongated
Undulating
straight
C. microcarpum Borcszcz.
Not observed
Free at base,
ovate
Not observed
Broadly
rectangular to
irregular
Irregular
C. tetrapterum Jaub. &
Spach
main
dendricular vein
3 inner larger,
ovate outer
angular
Occasionally
anastomosing &
branching
Elongated to
rectangular
Straight
CALUGONUM L.
C. comosum L'Herit.
main vein
"The Asiatic plants are controversial, as either several or only one species arc recognized. Some authors have
maintained Tovarajiliformis (Thunb.) Nakai and T. neqfiliformis (Nakai) Nakai (Hara, 1962) or treated the
latter as a variety of l'olygonumjiliforme Thunb. (Li, 1952).
Hooker (1886) reduced the species to synonymy of Polygonum virginianum L., as did Steward (1930), who
recognized it as a variety of Tovara virginiana Adans.
hSteward ( 1930) considered Polygonum sieboldii to be hardly distinct from P. sagittalum and has included it in
the synonymy of the latter.
"Fresh material of Polygonum weyrichii was unfortunately male-sterile, which limits the morphological value of
the flowers in the present study. A. P. Conolly (personal communication) mentions long filaments, acute
perianth-segments and eight rounded nectaries for the male flowers; the female has short aborted stamens with
perianth-segments rounded at the tip.
We were able to investigate a specimen described as l'olygonum savatieri Nakai, which is to be considered a
synonym of P. weyrichii F. Schmidt. Petrop. var. alpinum Maxim. ex Franch. & Sav. This was male-fertile.
dThe species is variable in relation to its wide distribution. Its taxonomy is confused, as P. angustifolium Pallas
( = P. polymorphum Ledeb., or P. laxmannii Lepech.) has been referred to P. alpinum All. in one case, and to
P. angustifolium Pall. in another. We found very little difference between P. angustifolium and P. alpinum and
here follow Steward ( 1930) in recognizing a single species.
GENERIC LIMITS IN POLYGO.NUM
6
7
8
9
P5A8G3
Filiform, with
expanded base I
± same length
as 0
Outer slightly
higher, adnatc
on receptacle
Deep,
longitudinal to
random striae
P5A8G3
In ring around
ovary, 0 behind
I
Short random
striae
P4A6G2, T A
vanished with
IG
Inner larger all
with dilated,
subulate
filaments
Inner larger,
gradually
narrowing to top
Dense,
longitudinal to
random striae
P5A6-8G3,
occasionally no
dedoublement in
OA
P5A8G3
Inner longer,
gradually
broadening
towards base
Abaxially fused
with tepals,
flattened,
broadened at
base
Strong, deep
longitudinal
striae
P5AI3G4
Random striae
P4-5AI2G4
Slightly
flattened to
tetraquetrous;
no distinction
between whorls
Free, circular to
flattened not
differing in
length
Inner slightly
longer,
cylindrical to
filiform, erect
P5-6AI2G4,
occasionally
double A & 6 P
0 pressed
against carpel, I
covering main
carpel surface
In ring, 0
inserted slightly
higher
365
10
II
Numerous, long
in tulis at
stamen base
Short, with
cuticle on either
side of stamen
base
Sequential
decrease in size
towards 0, in
ring
Continuous ring
around ovary
Dense layer
long, at filament
base
Not distinct in 2
whorls, 2 x 3
oppos. I & 3 x 2
oppos. 0 P
Continuous ring,
0 in pairs, I in
higher numbers
Long, in tufts at
stamen bases
Dense tufts at
base of filam<"nts
•Recently Hickman ( 1984) included several North American species within Po(ygonum douglasii, as the
differences between them were not convincing. We investigated two species which are referred toP. douglasii
by Hickman (P. coarctatum Dougl. ex Hook. = P. douglasii ssp. spergulariiforme (Meissn. ex Small) Hickm. and
P. douglasii (var.?) montanum Small, which is not mentioned by Hickman.
rwe investigated two specimens: Porygonum scandens L. and P. scandens var. dentato-alatum (F. Schmidt Pt>trop.)
Maxim. ex Franch. & Sav. Holub (1970) and some authors before him consider the latter to be a distinct
species on the basis of the winged perianth with dt>ntatt> margin (st>e also Steward, 1930). The difft>renc<"s do
not seem to be significant, and we treat the taxa under the same name. However, in var. dentato-alatum, no
trichomes were found.
gWe only investigated pistillate flowers, as no male-fertile material was available. Specimens of Porygonum
japonicum, as well as the dwarf variant described as P. compactum Hook. fil., were invf"stigated (see Steward,
1930; Conolly, 1977).
Porygonum sachalinense provided both staminate and pistillate flowers. The pistillate flowers had inserted
filamt>nts, I mm long, with a swollen base. The staminate flowers had exserted filaments, 2 mm long, with a
less swollen base.
"Synonymous with Porygonella polygama (Vent.) Engelm. & Gray (Horton, 1963).
366
L.-P. RONSE DECRAENE AND J. R. AKEROYD
APPENDIX 2
Provenance and .ryno1rynry
rif specimens investigated
Specimens are listed together with some relevant synonyms.
New combinations are made only where a nomenclatural change is requested by the vacancy in the
literature and when a species is fully identified. New combinations are indicated by bold-face type.
Cases of doubt are left open as more thorough investigations are needed.
Ls, Lb, Le and Lm indicate L.-P.R,D.'s collections of pickled material. Voucher specimens, except material
borrowed from other herbaria, are kept at the Botanical Institute in Leuven, Belgium. RNG = Reading,
K = Kcw and LV = Leuven.
PERSICARIA Mill.
Persicaria macula/a (Raf.) Love & Love
SYNONYM: Polygonum persican'a L.
Bruges, 2 vii 1986, Ronse Decraene 24 Lb, FAA.
Persicaria nodosa ( Pers.) Opiz
SYNONYM: Polygonum nodosum Pers. var. erectum, Lousley ( RNG).
Persicaria pennsylvanica (L.) Gomez de Ia Maza
SYNONYM: Polygonum pennsylvanicum L.
Alien, W. Kent, 1975, Lousley (RNG).
Persicaria minus ( Huds.) Opiz.
SYNONYM: Polygonum minus Huds. var. elatum Moss, W. Sussex, 1938, Sandwith (K).
Persicaria hydropiper (L.) Opiz.
SYNONYM: Po/ygonum hydropiper L.
Devon, Dartmoor, 1982, Souster (RNG).
Persic aria amphibia (L.) S.F. Gray.
SYNONYM: Polygonum amphibium L.
Morocco, 1974, Humphries, Richardson, Jury & Mullin 1039 (RNG).
Persicaria barb ala (L.) Hara
SYNONYM: Polygonum barbatum L.
China, Shui Mei river, Toam distr., Hainan, 1927, Tsang 666 (K).
Persicaria perfoliata (L.) H. Gross
SYNONYM: Polygonum perfoliatum L.
Japan, Hunshu, Pref. Osaka, Kunanoda, 1965, Togashi 700 (K).
Persicaria sieboldii (Meissn.) Ohki
sYNONYMS: Po{ygonum sieboldii Meissn., Persicaria sagitta/a (L.) H. Gross
Japan, Hondo, Koshigaya in Musashi, 1950, Ohwi 110 (K.).
Persicaria strigosa (R. Br.) Nakai
SYNONYM: Po{ygonum strigosum R. Br.
India, Madras, presented 1871, Wight (K).
Persicaria peduncularis (Wall. ex Meissn.) Nemoto
SYNONYMS: Po{ygonum pedunculare Wall. ex Meissn., Po{ygonum strigosum R. Br. var. pedunculare (Wall. ex
Meissn.) Steward: var. anguslissimum HKF, India, Sambalpur, 1940, Mooney 1475 (K.)
Pmicaria limbata (Meissn.) Hara
SYNONYM: Polygonum limbatum Meissn.
Clulkana, near Lakarumpour, 1846, Herb. Hookerianum (K).
Persicaria senegalensis (Mcissn.) Sojak
sYNONYM: Po{ygonum senegalense Meissn.
England, wool alien, 1953, Lousley 53110152 (RNG); Senegal, Lac de Guiers, M'bane, 25 xii 1986, Ronse
Decraene 44 Ls, FAA.
Persicaria lomenlosa (Willd.) Sasaki
SYNONYM: Po{ygonum tomentosum Willd.
India, Dacca Station, 1868, Clarke 8144 (K).
GENERIC LIMITS IN POLYGONVM
367
Persicaria orienta/is (L.) Spach.
SYNONYM: Polygonum orientale L.
Iter chinense, Yunnan, 1914, Schneider 2741 (K); Nat. Bot. Card. of Belgium, Meise, 28 viii 1987, Ronse
Decraene 207 Lm, FAA.
Persicaria capitola (Buch.-Ham ex D. Don) H. Gross
SYNONYM: Polygonum capitalum Ham.-Buch. ex D. Don
A~ores, Faial, 1984, L. C. Jury 9 (RNG); Royal Botanic Gardens, Kew, 267-72.06329, 13 v 1986, Ronse
Decraene 18 Le, FAA.
Persicaria runcinata (Buch.-Ham. ex D. Don) Masamune
SYNONYM: Po/ygonum runcinalum Ham.-Buch. ex D. Don
Bhutan, Guto-La To Guetza, 1938, Gould 410 (K).
Persicaria glacialis (Meissn.) Hara Felici Garkwal, 1925, Gamble 24246 (K).
Per sicaria chinensis (L.) Nakai
SYNONYM: Polygonum chinense L.
Malaya, Pahany, Cameron Highlands, 1985, Bowen 3979 (RNG).
Persicaria virginiana (L.) Gaertn.
SYNONYM: Polygonum virginianum L.
USA, Philadelphia, 1983, Bowen U5 (RNG); Jard. Bot. Bordeaux, cult. Bruges, 4 ix 1987, Ronse Decraene 217
Lb, FAA.
Persicaria neojiliformis Ohki
SYNONYMS: Po/ygonum neojiliforme Nakai, Persicariafiliformis Nakai
China, Lushan, Kiangsi, 1975, Cheng 80 (K); Nat. Bot. Card. of Belgium, Meise, 5 x 1986, Ronse Decraene 34
Lm, FAA.
Persicaria sericea (Pall.) H. Gross
SYNONYM: Polygonum sericeum Pall.
Cult. Cambridge 52.96, 1907 (K).
PeraictJria hookeri (Meissn.) Ronse Decraene, comb. nov,
BASIONYM: Po/ygonum hookeri Meissn., Ann. Sci . .Nat., ser. 5, 6: 352 (1866).
Japan, Karisawa Asama, 1930, presented by Greatrex 1951 (K).
Persicaria po/yslachya (Wall.) H. Gross
SYNONYM: Po/ygonum polystachyum Wall. ex Meissn.
Reading Bot. Card., xi 1985, Ronse Decraene 15 Le, FAA.
Peraic•ri• camp•••lattJ (Hook. til.) Ronse Decraene, comb. nov.
BASIONYM: Polygonum campanulatum Hook. til., Fl. Br. Ind., 5: 51 (1886).
L.-P.R.D.'s garden, Bruges, 18 ix 1985, Ronse Decraene 12 Lh, FAA.
Peraict1ri11 tripterocarpa (A. Gray) Ronse Decraene, comb. aov.
BASIONYM: Po/ygonum lripterocarpum A. Gray, Ann. Rep. Smiths. Insl., 1867: 453 (1867).
SYNONYM: Polygonum pawlowskyanum Glehn.
Dupl. ex Herb. Hart. Bot. lmper. Petropolitani, 1875, .Nowicz (K).
Pernc•ri• artgJUtijolia (Pall.) Ronse Decraene, comb. nov.
BASIONYM: Polygonum angustifolium Pall., Reise, 3: 230 ( 1776).
SYNONYMS: Persicaria alpina (All.) H. Gross, Polygonum polymorphum Ledeb.
Royal Bot. Card., Kew, 00069.50009, 5 vi 1986, Ronse Decraene 23 Le, FAA; Herb. Lousley, Aberdeen, 1968,
Pagel (RNG); var. laxmannii, Royal Bot. Card., Kew, 006950025, 5 vi 1986, Ronse Decraene 21 Le, FAA;
France, St. Martin-Vesubie, Alpes maritimes, 1972, de Witte 17214 (LV).
Pmicaria divaricala (L.) H. Gross
SYNONYM: Polygonum divaricalum L.
China, Chark'ar Hsiao Wutaishan, Tangchisze, 1930, Kung 1165 (K).
Peraicari11 weyriclaii (F. Schmidt Petrop.) Ronse Decraene, comb aov.
BASIONYM: Polygonum weyrichii F. Schmidt Petrop. ex Maxim., Mlm. Acad. Sci. St. Pltersb., 9: 234 ( 1859).
Oxford Bot. Card., 4 vi 1986, Ronse Decraene 19 Le, FAA; var. alpina Maxim. ex Franch. & Sav. (synonym:
Polygonum savalieri Nakai), japan, Karisawa Asama, 1930, presented by Greatrex 1951 (K).
Persicaria historta (L.) Sampaio
SYNONYM: Polygonum bislorta L.
W. Kent, Darenth, 1931, Lous/ey 1673 (RNG); L.-P.R.D.'s garden, Bruges, cultivar, 9 v 1987, Ronse Decraene
128 Lb, FAA.
368
L.-P. RONSE DECRAENE AND J. R. AKEROYD
Perllicaria vivipara (L.) Ronse Decraene, comb. aov.
BASIONYM: Polygonum viviparum L., Sp. Pl.: 360 ( 1753).
Norway, Head ofSordaen, 1961, Schilling /4 (K).
Perllicaria affinis (D. Don) Ronse Decraene, comb. aov.
BASIONYM: Polygonum affine D. Don, Prodr. Fl . .Nepal.: 70 (1825). cv. Superbum; Reading Bot. Gard. 40434, I
v 1986, Ronse Decraene 20 Le, FAA.
Persicaria vacciniifolia (Wall.) Ronse Decraene, comb. aov.
BASIONYM: Polygonum vacciniifolium Wall., ex Meissn. in W. Pl. As. Rar., 3: 54 ( 1832).
L.-P.R.D.'s garden, Bruges, 28 ix 1985, Ronse Decraene /3 Lb, FAA.
Persicaria amplexicaulis (D. Don) Ronse Decraenc, comb. aov.
BASIONYM: Polygonum amplexicaule D. Don, Prodr. Fl . .Nepal.: 70 (1825).
v~r. oxyphyllum, Royal Botanic Gardens, Kew, 13 x 1985, Ronse Decraene /4 I.e, FAA.
FAGOPYRUM Mill.
Fagopyrum esculentum Moench.
SYNONYM: Polygonumfagopyrum L.
USA, Pennsylvania, Monroe Co., Delaware Water Gap, 1969, Brumbach 6902 ( K); Reading Bot. Gard. 16
viii 1986, Ronse Decraerze 30 Le, FAA.
dibot~ys (D. Don) Hara
sYNONYMS: Polygonum dibotrys D. Don, Fagopyrum rymosum (Trev.) Meissn.
Nepal, cult. in Hyde Park, 1933 (K); Herb. Hort. Kew, 1917, Bees s.n. (K).
Fagopyrum
Fagopyrum leptopodum (Dids) Hedb.
SYNONYM: Polygonum leptopodum Diels
Iter chinense, Yunnan, 1914, Schneider 20/5 (K).
Fagopyrum giraldii (Dammer & Diels) Haralds.
SYNONYM: Ptero~ygonum giraldii Dammer & Diels ex Diels
North China, 1918, Licent 4078 (K).
HARPAGOCARPUS Hutch. & Dandy
Harpagocarpus srwwdenii Hutch. & Dandy
SYNONYM: Fagopyrum ciliatum Jacques-Felix.
Tanganyika, 1960, Kerfoot 1546 (K).
KOENIG/A L.
Koenigia islandica L.
Greenland, ex Museum Botanicum Hauniense, 1976, .Nielsen 69 (RNG).
Koenigia delicatula (Meissn.) Hara
SYNONYM: Polygonum delicatulum Meissn. f. brevistyla (Meissn.) Hcdb., Tibet, Upper Chambi valley, 1938,
Gould (K).
Koenigia pilosa Maxim.
SYNONYM: Polygonum pilosum Maxim. ex Forbes & Hemsley
China, Szechuan, Sung Pan Hsicn, 1928, Fang 4419 (K).
Koenigia nummularifo/ia ( Meissn.) Mesicek & Sojak
SYNONYM: Polygonum nummularifolium Meissn.
Kumain, Ralam valley, 1884, Duthie 3337 (K).
Koenigiaforrestii (Diels) Hedb.
SYNONYM: Polygonum forrestii Diels
China, Yunnan, lsekon, 1912, Monberg 82 (K).
Koenigiafilicaulis (Wall. ex Meissn.) Hedb.
SYNONYM: Polygonumfi/icau/e Wall ex Meissn. in Wall.
India, Assam, Delei valley, 1929, Kingdon Ward 86/2 (K).
POLYGONUM L.
Polygonum aviculare L.
subsp. aequale (Lindm.) Aschers & Graebn., Belgium, Bruges, 28 vi 1986, Ronse Decraene 25 Lb, FAA.
GENERIC LIMITS IN POLYGO.NUM
369
Polygonum scoparium Req. ex Loisel.
Reading Bot. Gard., cult. (garden clone: see Akeroyd & Rutherford, 1987), I xi 1985, Ronse Decraene 16 Le,
FAA.
Polygonum floribundum Schlecht. ex Sprengel
USSR, Prov. Seratov, 1924, Kasakeviez (K).
Polygonum oxyspermum C. A. Meyer & Bunge ex Ledeb.
subsp. raii (Bab.) D. A. Webb & Chater; 1983, Jury & Rumsey 4650 (RNG).
Polygonum patulum Bieb.
Afghanistan, Tashkargan, 1966, Furse 7793 (K).
Polygonum plebejum R. Br.
India, Belgain, Karnataka, 1980, Kameswara Rao 27 (K).
Polygonum maritimum L.
Portugal, Barboa Sines, 1981, Grandvaux 13573 (RNG).
Polygonum californicum Meissn.
USA, California, Stanislaus Co., 1937, Hoover 2392 (K).
Polygonum douglasii Greene
SYNONYMS: Polygonum spergulariiforme Meissn. ex Small, P. coarctatum Dougl. ex Hook. fil.
USA, Saturne Island, Oregon Boundary Commission, 1858, Lyall (K); USA, Explor. of Montana &
Yellowstone Park, 1897, Rydberg & Bessey 5364 (K).
Polygonum molliaeforme Boiss.
Iran, Denawand, Iter Persicum alterum, 1902, Bornmiiller 8181 (K).
Polygonum afromontanum Greenway
Ethiopia, Kaffa Prov., 1972, Danish-Ethiopian Botanical Expedition 1972-1973 1622 (K).
FALLOPIA Adans. emend. Ronse Decraene
Fallopia aaelaalinensia (F. Schmidt Petrop.) Ronse Decraene, comb. nov.
BASIONYM: Polygonum sachalinmse F. Schmidt Petrop. ex Maxim., Mim. Acad. Sci. St. Pitersb., 9: 233 (1859).
SYNONYM: Reynoutria sachalinmsis (F. Schmidt. Petrop.) Nakai
England, Oxon, Marslow adv., 1902, Druce (LV), male-sterile; England, Cirencester, 1985, Leg. Bail~y,
Alcohol, male and female flowers.
Fallopiajaponica (Houtt.) Ronse Decraene, comb. nov.
BASIONYM: Reynoutriajaponica Houtt., Hand/. Regn. Veg., 8:639 t. 51 F. I (1777).
SYNONYM: Polygonum cuspidatum Sieb. & Zucc.
var. compacta (Hook. fil.) Buchheim; L.-P.R.D.'s garden, Bruges, II xi 1985, Ronse Decrame 10 Lb, FAA
(male-sterile; the var. is discussed by Conolly, 1977); L.-P.R.D.'s garden Bruges, II ix 1985, Ronse
Decraene 11 Lb, FAA (male-sterile); S.W. Glamorgan, Oystermouth, 1909, Barley 1218 B (LV).
Fallopia scandens (L.) Holub
SYNONYM: Polygonum scandens L.
USA, Philadelphia, 1983, Bowen U5 (RNG); var. dentato-alatum (F. Schm. Petrop.) Maxim. ex Franch. &
Sav., China, Shantung Prov., 1930, Chiao 3140 (K).
Fallopia convolvulus (L.) A. Love
SYNONYM: Polygonum convolvulus L.
1981, White 49 (RNG); Belgium, Bruges, 28 vi 1986, Ronse Decraene 26 Lb, FAA.
Fallopia aubertii (L. Henry) Holub
SYNONYM: Polygonum aubertii L. Henry
China, Ala Mountains, Ning-Hsia, 1933, Pai 1/0 (K).
Fallopia baldschuanica (Regel) Holub
SYNONYM: Po£ygonum baldschuanicum Regel
19.58, Watson 47 (RNG); Reading, cult., 21 vi 1986, Ronse Decraene 27 Le, FAA.
Fallopia pterocarpa (Meissn. in Wall.) Holub
SYNONYM: Polygonum pterocarpum Wall. ex Meissn. in Wall. Sikkim, Darjeeling, 1880, Gamble 8520 (K).
POLYGONELLA Michx
Polygonella parksii Cory
USA, Texas, Leon Co., Normangle, Hilltop lakes resort, 1968, Correll & Correll 36649 (K).
L.-P. RONSE DECRAENE AND J. R. AKEROYD
370
Polygone/la polygama (Vent.) Engelm. & Gray
SYNONYMS: Polygonum polygamum Vent., Polygone/la parviflora Michx, Polygone/la parvifolia (Michx) Raf.
USA, N. Carolina, Brunswick Co., Orton Plantation Gard., 1940, Gotifrey 1046 (K).
Polygone/la parviflora Michx
USA, Florida, Palm Beach, 1895, Curtiss 5525 (K).
Polygone/la articulata (L.) Meissn.
SYNONYM: Polygonum articulatum L.
USA, Virginia, Nansemond Co., 1939, Long 11563 (K).
Polygonella americana (Fisch. & Mey.) Small
USA, Arkansas, Hot Springs Co., Malvern, 1915, Palmer 8473 (K).
OXYGONUM Burch.
Ovgonum dregeanum Meissn.
var. canescens Send., S. Africa, Pretoria, 1904, Burtt Da!!J 2528 (K).
Oxygonum delagoense Kuntze
S. Africa, Oppermansdrifdam, Bultfontein, 1974, O'Connor 79 (K).
Ovgonum alatum Burch.
S. Africa, Cape Prov., lrquatown, 1920, Pole-Evans 27 (K).
PTEROPYRUM Jaub. & Spach.
Pteropyrum olivieri J au b. & Spach.
Iran, ncar Teheran, 1963, Bowles Scholarship Bot. Exped. 2001 (K).
Pteropyrum scoparium Jaub. & Spach.
Sultanate of Oman, Bid Bid service stn., 1982, Maconochie 3273 (K).
Pteropyrum aucheri Jaub. & Spach.
Iraq, Sulermanrya, 1934, AI-Raddi 5282 (K).
ATRAPHAXIS L.
Atraphaxis buxifo/ia (Bieb.) Jaub. & Spach.
SYNONYM: Polygonum buxifolium Bieb.
USSR, Prov. Tiflis, 1909, Woronow & Schelkownikow 3 (16) IV (K).
Atraplt.axis spinosa L.
USSR, Herb. nom. V. L. Komarovi, 1962, Avetisian (RNG).
Atraphaxis billardieri J au b. & Spach.
var. toumifortii (Jaub. & Spach.) Cullen, Turkey, Prov. Erzerum, Karaugan, Horasan, 1957, Davis & Hedge
D. 30731 (K).
Atraphaxis seravshanica Pavl.
USSR, Turcomania, 1975, Beliavina & Proskwiakova 134 (RNG).
CALLIGONUM L.
Calligonum comosum L'Herit.
Arabia, Oman, 1951-52, Oldfield /83 (K).
Calligonum microcarpum Borszcz.
USSR, Turcomania, 1975, Beliavina & Provskwiakova /36 (RNG).
Calligonum tetrapterum Jaub. & Spach.
Kuwait, Ahmadi, 1981, Green, Hedge & Wickens 4 (K).
APPENDIX 3
Key to genera and sections
7
Nectaries present as conspicuous mamillae around the stamens; stamens not enlarged at the base,
all about the same size and without papillae on the filaments; reduction of stamens affecting
inner whorl; tepa! venation trifid, with rectangular to elongate epidermal cells and smooth or
GENERIC LIMITS IN POLrGONUM
371
shallow striation; outer tepals rarely winged, keeled or angular, often smaller than inner or absent
tribe Persicarieae
2 Tepals almost free, remaining small in fruit; number of floral parts constant; filaments winged;
habit twining or erect; nectaries free, globular and stalked; embryo embedded in endosperm
within the achene
Fagopyrwm
2 Tepals usually fused for up to 1/2 or more, enclosing the fruit at maturity; number of floral parts
constant or reduced; filaments not winged; habit erect; nectaries free or fused with stamen bases,
not stalked; embryo in one angle of the achene
3 Perianth 3- to 5-partite; flower with tendency to trimery; nectaries confluent into disc, associated
with club-shaped papillae
Koeraigia
3 Perianth usually 5- or 4-partite; nectaries free, fused with the inner stamens or confluent at the
base; papillae cylindrical and erect
. PerBicaria
4 Tepals almost free or slightly fused at the base; number of floral parts mostly constant
5 Styles 3, free and elongate; flowers in solitary and terminal spike; tepals and stamens erect and
elongate; inner nectaries confluent with inner filament bases
PerBicaria section Bistorta
5 Style I, simple and trifid; flowers in diffuse panicles; tepals spreading, outer stamens erect or
curved; nectaries broad and confluent at the base
PerBicaria section Aconogonon
4 Tepals fused for more than 1/3 of their length into a cupular structure; number of floral parts
often reduced
6 Style I, bifid or trifid; outer stamens 4-8, inserted clearly higher than inner; nectaries free,
globular; papillae usually present .
. PerBicaria section PerBicaria
6 Style 2-partite at the base, persistent, with recurved tips; outer stamens not inserted much
higher than inner; perianth 4-partite; stamens 5; nectaries obtuse, confluent, with few or
no papillae .
. Persicaria section ToJJara
7 Nectaries absent as conspicuous mamillae around the stamens; Stamens often inflated and enlarged
at the base, inner larger, sometimes with papillae at the base of the filaments; reductions of
stamens affecting the outer whorl; tepa! venation dendricular or anastomosing, with irregular to
elongate epidermal cells and strongly papillose striation; outer tepals often winged, keeled or
angular, smaller or larger than inner
tribe Polygoneae
7 Stamen number mostly constant or increased; conspicuous papillae present around the filaments;
inner stamens not or seldom dilated at the base; herbs, climbers or much branched shrubs
8 Outer tepa! segments smaller than inner, neither keele<i nor winged; tepa! venation forming an
anastomosing network by abundant branching; herbs or shrubs
9 Erect, much-branched shrubs; tepals not tightly enclosing ovary
10 Stamens 12 or more; papillae long, conspicuous at base of filaments.
Calligoraum
10 Stamens 6-8; papillae long, short or absent
II Tepa! venation dendricular, profusely branching; papillae absent or inconspicuous;
.Atraplaaxis
stamen bases inflated .
II Tepa! venation limited to central, anastomosing core; papillae numerous and conspicuous;
stamen bases not inflated .
Pteropyrwm
9 Herbs; tepals elongate, tightly fused around ovary
. O~ygonum
8 Outer tepa! segments keeled or winged, larger than inner; tepa! venation dendricular; climbers
or herbs
Fallopia
12 Perianth enlarging in fruit; stigma fimbriate; habit erect; dioecious
Fallopia section Reynoutria
12 Perianth usually not enlarging in fruit; stigma capitate or peltate; habit twining; not
dioecious
13 Papillae numerous, covering filaments; stigma peltate; inflorescence paniculate
Fallopia section Sarmentosae
13 Papillae few or none, scattered around filaments; stigma capitate; inflorescence laxly
Fallopia section Fallopia
paniculate or a cluster of flowers
7 Stamen number often variable through reduction of outer stamens; inner stamens often strongly
enlarged at the base; no papillae present around the filaments; low shrubs or herbs
14 Number of floral parts mostly constant; inner filaments often abruptly widening at the base;
tepals with single, non-branching vein; inflorescence racemose
Polygonella
15 Inner filaments with two clear lateral teeth; inner tepals entire Polygonella section Polygonella
15 Inner filaments not so, all alike; inner tepals fimbriate
Polygonella section Tlaysanella
14 Number of floral parts often reduced through the outer stamens; inner filaments gradually
inflated at the base; tepals with single dendricularly branching vein; flowers in axillary
clusters
Polygonum
16 Outer tepals with well developed keel; dendricular venation with two clearly devdoped
laterals; epidermal cells rectangular with elongated striation .
. Polygonum section Teplais
16 Outer tepals at most angular; dendricular venation with small laterals; epidermal cells
Polygonum section Polygonum
irregular with deep network of striae
Harpagocarpus has not been included in the above key, as a more detailed investigation of more material is
needed to determine its position in or near Fagopyrum.