Annals of Botany Page 1 of 17
doi:10.1093/aob/mcq010, available online at www.aob.oxfordjournals.org
Spikelet structure and development in Cyperoideae (Cyperaceae): a monopodial
general model based on ontogenetic evidence
Alexander Vrijdaghs1,*, Marc Reynders2, Isabel Larridon2, A. Muthama Muasya3, Erik Smets1,4
and Paul Goetghebeur2
1
Laboratory of Plant Systematics, Institute of Botany & Microbiology, K.U. Leuven, Kasteelpark Arenberg 31, B-3001 Heverlee
(Leuven), Belgium, 2Research Group Spermatophytes, Department of Biology, Ghent University, K.L. Ledeganckstraat 35,
B-9000 Gent, Belgium, 3University of Cape Town, Department of Botany, Private Bag, 7700 Rondebosch, South Africa and
4
National Herbarium of the Netherlands, Leiden University Branch, Leiden, The Netherlands
* For correspondence. E-mail alexander.vrijdaghs@bio.kuleuven.be
Received: 23 October 2009 Returned for revision: 9 December 2009 Accepted: 18 December 2009
† Background and Aims In Cyperoideae, one of the two subfamilies in Cyperaceae, unresolved homology questions about spikelets remained. This was particularly the case in taxa with distichously organized spikelets and in
Cariceae, a tribe with complex compound inflorescences comprising male (co)florescences and deciduous female
single-flowered lateral spikelets. Using ontogenetic techniques, a wide range of taxa were investigated, including
some controversial ones, in order to find morphological arguments to understand the nature of the spikelet in
Cyperoideae. This paper presents a review of both new ontogenetic data and current knowledge, discussing a
cyperoid, general, monopodial spikelet model.
† Methods Scanning electron microscopy and light microscopy were used to examine spikelets of 106 species
from 33 cyperoid genera.
† Results Ontogenetic data presented allow a consistent cyperoid spikelet model to be defined. Scanning and light
microscopic images in controversial taxa such as Schoenus nigricans, Cariceae and Cypereae are interpreted
accordingly.
† Conclusions Spikelets in all species studied consist of an indeterminate rachilla, and one to many spirally to
distichously arranged glumes, each subtending a flower or empty. Lateral spikelets are subtended by a bract
and have a spikelet prophyll. In distichously organized spikelets, combined concaulescence of the flowers and
epicaulescence (a newly defined metatopic displacement) of the glumes has caused interpretational controversy
in the past. In Cariceae, the male (co)florescences are terminal spikelets. Female single-flowered spikelets are
positioned proximally on the rachis. To explain both this and the secondary spikelets in some Cypereae, the existence of an ontogenetic switch determining the development of a primordium into flower, or lateral axis is
postulated.
IN T RO DU C T IO N
In Cyperaceae, the larger of the two main clades comprises the
majority of cyperaceous genera. The smaller clade, sister to the
latter, is the mapanioid clade. Whereas previously four subfamilies were considered (Simpson et al., 2007), currently both
main clades have been recognized as the only two subfamilies
of Cyperaceae, namely Cyperoideae and Mapanioideae
(Fig. 1; Muasya et al., 2009). Cyperoid Cyperaceae can
easily be distinguished from Mapanioideae by the structure
of their flowers, which can be considered as typically monocotyledonous, actinomorphic and pentacyclic (two trimerous
whorls of perianth members, a trimerous diplostemonous
androecium and a trimerous gynoecium), although reduction
tendencies and many modifications occur. A cyperoid flower
usually originates in the axil of a subtending bract, called
glume (not homologous with glumes in Poaceae), with the
glumes and their flowers being organized in spikelets (e.g.
Haines and Lye, 1983; Goetghebeur, 1998; Vrijdaghs et al.,
2009). In contrast, a typical mapanioid reproductive unit
exists comprising an ontogenetic apex with a single, terminal
gynoecium, and lateral glume-like scales which may or not
be positioned opposite a stamen. In the flowers of most
mapanioid species, ‘empty’ scales occur in between the terminal gynoecium and the more proximally positioned stamens
(Haines and Lye, 1983; Goetghebeur, 1998). Because of this
unusual (synapomorphic) organization, floral and spikelet
structure remain to be clarified in mapanioid Cyperaceae.
Cyperoid spikelets as units of inflorescence
A cyperoid inflorescence has been described as a compound
multiple spike because of the indeterminate nature of the ultimate inflorescence units (Kukkonen, 1994) or as a compound,
paniculate inflorescence (Raynal, 1971), essentially a panicle
of spikelets (Goetghebeur, 1998), where spikelets functionally
replace the individual flowers of a panicle as defined by
Weberling (1992). Therefore, the term ‘paniculodium’ was
proposed for a cyperaceous panicle (Kukkonen, 1994;
Vegetti, 2003). Usually, each branch of the inflorescence is
subtended by a primary or involucral bract, and has an adaxially situated prophyll (between the new branch and its relative
main axis or rachis). Modifications and reduction tendencies,
including Troll’s principle of variable proportions (Troll,
1959), have resulted in a wide range of derived inflorescences
# The Author 2010. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
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Page 2 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Priorium serratum
Juncaceae
Outgroup
Mapanioideae
Subfamily Mapanioideae
Trilepedieae
Subfamily Cyperoideae
Cladieae
Schoeneae 5: Gymnoschoenus
Cryptangleae
Bisboeckelereae 1
Bisboeckelereae 2
Sclerieae
Schoeneae 1: Carpha
Schoeneae 2: Tetraria thermalis
Schoeneae 3: Capeabelus
Schoeneae 4: Schoenus nigricans
Rhynchosporeae
?: Khaosokia
Dulicheae: Dulichium, Blysmus
Scirpeae 1: Eriophorum, Scirpus
Scirpeae 2: Trichophorum
Cariceae: Carex
Abildgaardieae
Eleocharideae
Fuirenese 1: Fuirena
Fuirenese 2: Bolboschoenus
Fuirenese 3: Schoenoplectus
Fuirenese 4: Schoenoplectiela
Cypereae 1: Ficinia
Cypereae 2: Cyperus s.l.
F I G . 1. Simplified cladogram of Cyperaceae, adapted from a strict consensus tree from Muasya et al. (2009). The studied species belong to the taxa coloured in
white.
in Cyperoideae, varying from indeterminate spikes of spikelets
and contracted pseudolateral capitate inflorescences to anthelas
of spikelets or, as Kukkonen (1994) correctly called them,
‘anthelodia’ (Figs 2 and 3; Raynal, 1971; Haines and Lye,
1983; Goetghebeur, 1998; Vegetti, 2003; Guarise and
Vegetti, 2008). Within the inflorescence, primary branches
are subtended by primary or involucral bracts. In several
genera, higher order branches are subtended by the prophyll
of the relative main axis (Meert and Goetghebeur, 1979;
Goetghebeur, 1986).
The structure of a cyperoid spikelet
Cyperoid spikelets are the ultimate branches of the inflorescence, acting both as a morphological and as a functional unit
(Fig. 4). Consequently, a spikelet consists of a spikelet axis or
rachilla, and few to numerous spirally to distichously arranged
glumes, each subtending (or not) a single, bisexual or unisexual flower (Fig. 5; e.g. Eiten, 1976; Kukkonen, 1994;
Goetghebeur, 1998). In Cyperoideae, spikelets tend to take
over the flower function, as in the flower-like inflorescences
in Asteraceae and some Euphorbiaceae. Moreover, taxa such
as Ascolepis, Kyllinga, Lipocarpha, Queenslandiella, species
of Torulinium (¼Cyperus), Carex and Uncinia, and many
species belonging to the tribe Cypereae (sensu Goetghebeur,
1998) which were formerly classified in a distinct genus
Mariscus, have spikelets that are deciduous as a whole
(Nees, 1835, p. 286; Larridon et al., unpubl. res.).
According to Weberling’s typology (1992), the terminal spikelet of the main axis is a florescence and spikelets terminating
lateral axes are co-florescences (Vegetti, 2003). The first scale
on a lateral spikelet is a typical prophyll: situated adaxially and
therefore often referred to as ‘addorsed prophyll’ (e.g.
Kukkonen, 1994), usually two-keeled and not subtending
a flower, except in Dulichieae and Cariceae sensu
Goetghebeur (1998), where the prophyll forms a perigynium
or utriculus around the female flower. The next glumes
subtend (or not) a flower. The internode between the prophyll
and the second glume, called an epipodium, is often elongated
(e.g. Haines and Lye, 1983; Goetghebeur, 1986). A hypopodium, the internode between the bract subtending the spikelet
and the prophyll, is usually absent (Fig. 6). Spikelets laterally
positioned on a rachis are each subtended by a bract (Figs 6
and 7).
Many cyperoid species, however, have inflorescences with
lateral spikelet clusters, in which several spikelets occur in
the axil of a single subtending bract, as in Cyperus luzulae
(Fig. 8). Guarise and Vegetti (2008) made an elaborate typological study of spikelet clusters in Cyperus. Spikelet clusters
probably originate from a kind of dédoublement from the original primordium in the axil of the subtending bract, resulting in
serial axillary buds. In other cases, prophyll branching occurs
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Page 3 of 17
= Terminal spikelet (no subtending bract, no prophyll)
A
= Lateral spikelet (subtending bract, prophyll)
= Spikelet (subtending bract and prophyll not shown)
= Spikelet subtending bract
= Rachis
= Spikelet prophyll
B
C
D
F I G . 2. Schematic representation of a typical cyperoid panicle of spikelets or paniculodium, and some possible modifications of it.
paniculate
capitate
anthelate
compound spike
capitate
capitate
F I G . 3. Photographs illustrating inflorescence variation in Cyperoideae. From upper left- to lower right-hand corner: Dulichium arundinaceum (paniculate),
Cyperus haspan (anthelate), Rhynchospora latifolia (capitate), Eriophorum latifolium (capitate), Carex capitata (compound spike), Cyperus capitatus (capitate).
Page 4 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Scirpus sylvaticus
Eriophorum latifolium
Eleocharis palustris
Ficinia brevifolia
Fuirena ciliaris
Scirpoides holoschoenus
Distichous
Spiral
F I G . 4. Photographs of part of the inflorescence in Cyperus alternifolius (left) and in Lipocarpha chinensis (right), with in each a single spikelet encircled in red.
The single-flowered spikelet in L. chinensis is so reduced that the inflorescence as a whole takes over the spikelet function.
Cyperus congestus
Dulichium arundinaceum
Schoenus nigricans
F I G . 5. SEM images of spikelets at early developmental stage in nine different cyperoid species, illustrating spirally and distichously organized spikelets. The
two upper rows illustrate spikelets with a spiral arrangement of the glumes, the lower row spikelets with a distichous arrangement of the glumes. Spikelets in
Scirpus sylvaticus, Eriophorum latifolium, Fuirena ciliaris, Eleocharis palustris, Ficinia brevifolia and Scirpoides holoschoenus have spirally arranged
glumes, whereas spikelets in Cyperus congestus and Dulichium arundinaceum have distichously arranged glumes. This is also the case in Schoenus nigricans,
of which only the distal part of the spikelet is shown here, illustrating the metatopic displacement of the distal flower. The numbers (1 ¼ most recently originated)
indicate glumes (each with its flower primordium in the axil) at different stages of development. Red frame: shown in more detail in Fig. 14. Abbreviations: F,
flower primordium; G, glume; asterisk (*), rachilla apex.
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Page 5 of 17
Ra
G
P
B
Gp
Gp
1·5 mm
P
Epipodium
500 µm
B
Ra
Rl
F
G
Gp
F I G . 7. Photograph of part of the inflorescence in Cyperus alternifolius, in
which a group of spikelets is distichously placed on the rachis. The internodes
between the spikelets are so contracted that the spikelets become apparently
arranged digitately. Each lateral spikelet is subtended by a bract (B), and
has a short glume-like prophyll (P). The spikelets have many, distichously
arranged glumes, each subtending a flower. The spikelet terminating the
rachis is not subtended by a bract and does not have a prophyll. The prophyll
of a lateral axis carrying another, similar, partial inflorescence has an adaxially
situated swelling body (encircled). Abbreviations: B, bract subtending a spikelet; Gp, proximal glume; P, spikelet prophyll; black dotted line, rachis; red
dotted line, rachilla; encircled, swelling body at the base of a prophyll of a
lateral axis.
B
Epipodium
F I G . 6. Schematic representation of a typical cyperoid spikelet and corresponding SEM image of a spikelet in Pycreus polystachyos, growing in the
axil of a bract. The rachis and remnants of the spikelet-subtending bract are
coloured green. The tubular spikelet prophyll, with an adaxially situated swelling body or pulvinus at its base (arrowed), is coloured red. The prophyll envelops a long first internode or epipodium. Distichously arranged glumes, each
subtending a flower, are coloured purple. Protruding stigma branches are in
yellow. In the SEM image, the spikelet axis or rachilla is hidden by the
glumes. Abbreviations: B, bract subtending a spikelet; F, flower ( primordium);
G, glume; Gp, proximal glume; P, prophyll; Ra, rachis; Rl, rachilla; asterisk
(*), rachilla apex.
(Goetghebeur, 1998; Vrijdaghs et al., 2003). In some species,
at the base of the prophylls (of spikelets and/or inflorescence
branches), a swelling body or pulvinus is present (Figs 5 and
6; Haines, 1967). These play a role in the expansion of the spikelets, related to wind pollination. The formation of spikelet
clusters in Cyperus and allied genera is under investigation
(Larridon et al., unpubl. data).
In several genera, there is a tendency towards reduction of the
spikelets. In the highly derived Cypereae genus Lipocarpha,
reduction of spikelets is so advanced that the inflorescence as
a whole takes over the spikelet function (Figs 4; 17; 18;
Goetghebeur, 1986; Vrijdaghs, 2006). According to Timonen
(1998), in Cariceae, the spikelet concept is blurred by the male
reproductive units, always grouped in (co)florescences, as in,
for example, Carex capitata (Fig. 9). Timonen (1998) suggested
that the male ‘flowers’, each consisting of only three stamens
subtended by a glume-like bract, are actually extremely
reduced spikelets. Female flowers occur only in deciduous,
single-flowered spikelets subtended by a bract. Such a spikelet
was considered by Timonen (1993) to be a reduced lateral
spike, derived from a compound bisexual branch. Smith
(1967) reported that the determination of primordia in inflorescences in Carex can be explained by auxin- and kinetin-like
factors. A high level of auxin favours the development of a
lateral axis. If simultaneously the primordium is treated with
kinetin, it develops into a lateral spike. If not, the primordium
develops into a female spikelet. A low level of auxin determines
if a given primordium becomes a male flower.
Controversy about the monopodial or sympodial nature
of cyperoid spikelets
In the past, influenced by the euanthial or pseudanthial controversy, many discussions arose about the monopodial or
sympodial nature of the cyperoid spikelet. In these discussions,
cyperoid spikelets were compared with the reproductive unit in
Mapanioideae, as an argument in favour of the pseudanthial
interpretation (e.g. Celakovsky, 1887; Kern, 1962; Bruhl,
1995; Zhang et al., 2004; Richards et al., 2006). Bruhl
(1991) presented a comprehensive overview of the different
standpoints. However, Vrijdaghs et al. (2009) showed that
the rachilla, in a wide range of investigated cyperoid species,
is indeterminate with new glumes always originating laterally,
immediately below the rachilla apex. As a consequence, the
earliest floral ontogenetic stages always occur apically, with
the oldest flowers situated proximally. Hence, according to
Weberling’s (1992) typology, a lateral cyperoid spikelet can
be described as an open spike (Vrijdaghs et al., 2009).
According to Haines (1967), a spikelet terminating a culm
can be considered to be subtended by the bract subtending
the culm. In a similar way, the culm’s prophyll can be considered also to be the terminal spikelet’s prophyll. However,
Eiten (1976) saw bract and prophyll as structures which do
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
200 µm
Page 6 of 17
P
P
P
P
P
P
B
B
F I G . 8. Schematic presentation and SEM image of a serial spikelet cluster in Cyperus luzulae, subtended by a single, common bract. Each spikelet has its own
prophyll. Abbreviations: B, bract subtending a serial cluster of spikelets; P, spikelet prophyll.
Spike of spikelets
Male reproductive units
Female spikelets
spikelet, even when they are next to it.’ (Eiten, 1976, p. 82).
Goetghebeur (1986, 1998) preferred to describe terminal spikelets as spikelets without bract and prophyll and lateral spikelets as subtended by a bract and having a spikelet prophyll.
The current study presents a review of the current knowledge about cyperoid spikelets, and includes some original
ontogenetic scanning electron (SEM) and light microscopical
(LM) data leading to a general, monopodial cyperoid spikelet
model. Because our conclusions are based on over 8 years
of observations in a wide range of cyperoid genera
(Appendix 1), only a limited, highly illustrative selection of
observations is shown here and discussed. The spikelet
model allows all types of derived spikelets studied within
Cyperoideae to be interpreted in an unambiguous, logical,
standardized way.
Because of the large number of species and genera cited and
to keep the text readable, an alphabetical list of the species
including authorities is provided in Appendix 2.
MAT E RI AL A ND M E T HO DS
F I G . 9. Photograph of inflorescences in Carex capitata. Each inflorescence is
a spike of spikelets, terminated by a florescence consisting of male reproductive units (or a terminal male spikelet), with open rachis. In the proximal part
of the rachis, several spirally arranged female spikelets (encircled) occur.
not belong to the spikelet, precisely because in a culm with a
terminal spikelet the latter is separated from the bract and prophyll of the culm by the total length of the culm and all
branchings in between: ‘ . . . For this reason, the subtending
bract and prophyll, and the internode just below and just
above the prophyll, are not considered to be part of the
Spikelets of 106 species from 33 cyperoid genera (Fig. 1) were
examined at early and mature stages (Appendix 1), of which
only a representative selection of illustrative examples is presented here (Appendix 1, in bold type). Numbering of
glumes and subtended flowers was done from most recently originated (1) to oldest (n), in order to avoid abstract numbers in
spikelets with many and/or a variable number of (flowersubtending) glumes. Partial inflorescences were collected in
the field or in botanical gardens (Appendix 1) and immediately
fixed in FAA (70 % ethanol, acetic acid, 40 % formaldehyde,
90 : 5 : 5). Spikelets were dissected in 70 % ethanol under a
Wild M3 stereo microscope (Leica Microsystems AG,
Wetzlar, Germany) equipped with a cold-light source (Schott
KL1500; Schott-Fostec LLC, Auburn, NY, USA).
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Page 7 of 17
Scanning electron microscopy
To prepare the material for critical-point drying, it was
washed twice with 70 % ethanol for 5 min. Next it was
placed in a mixture (1 : 1) of 70 % ethanol and DMM
(dimethoxymethane) for 5 min. The material was then transferred for 20 min to pure DMM. Critical-point drying was
done using liquid CO2 with a CPD 030 critical-point dryer
(BAL-TEC AG, Balzers, Liechtenstein). The dried samples
were mounted on aluminium stubs using Leit-C. For SEM
observation, the material was coated with gold via an
SPI-ModuleTM Sputter Coater (SPI Supplies, West-Chester,
PA, USA). SEM images were obtained with a JEOL
JSM-6360 (JEOL Ltd, Tokyo, Japan) at the Laboratory of
Plant Systematics (K.U. Leuven), or with a JEOL JSM-5800
LV scanning electron microscope at the National Botanical
Garden of Belgium in Meise.
Light microscopy
Spikelets were embedded in LR White Resin (London Resin
Company Ltd, London, UK). The material was transferred
gradually from pure ethanol to pure LR White (the first step
over 1 h, all following steps over 4 h, starting with pure
ethanol, followed by pure ethanol/LR White mixtures in
decreasing volume proportions of 3 : 1, 2 : 1, 1 : 1, 1 : 2 and 1
: 3 and finally pure LR White. Polymerization was performed
in an oven at 60 8C over 48 h. In order to remove possible air
bubbles within the glumes, the material was treated in a
Branson 2210 Auction (Branson Ultrasonics B.V., Soest, The
Netherlands) ultrasonic cleaner, during the first two steps.
The embedded material was cut at 2.5 mm with a Microm
HM360 (Thermo Scientific, Walldorf, Germany) microtome.
Staining was done with toluidin blue 0.1 %, and subsequently
the slices were mounted using Eukittw (O. Kindler GmbH,
Freiburg, Germany). LM images were observed with a Leitz
Dialux 20 microscope (Wetzlar, Germany) and digital photographs were made with a PixeLINK (PL-B622CF, Ottawa,
Canada) camera.
R E S U LT S
All cyperoid spikelets studied have an indeterminate axis
(rachilla) with few to many glumes, each subtending (or not)
a flower. New glumes originate successively immediately
below the rachilla apex, as in Scirpus sylvaticus (Fig. 10).
The glumes are spirally to distichously arranged and this
organization may change in the course of spikelet development, as in Scirpus falsus, where newly formed, distally situated glumes are arranged distichously and more proximally,
the glume arrangement is spiral (Fig. 11). In many species,
the glumes become winged in the course of their development.
In all distichously organized species studied, wings are present
and decurrent, partially enveloping the lower, alternate flower.
In the SEM image of Cyperus laevigatus (Fig. 12), two successive flowers are visible, an older one to the front coloured red,
seen from the lateral– abaxial side, and an alternate, higher
positioned, younger, blue-coloured flower to the rear. The
wings (also in blue) of the glume subtending the ‘blue’
flower partially envelop the older, ‘red’ flower. The LM
*
G
100 µm
F I G . 10. SEM image of the distal part of a developing spikelet in Scirpus sylvaticus. Encircled in red are several glumes, each subtending a flower primordium at different developmental stages. Abbreviations: G, glume; asterisk (*),
rachilla apex.
*
50 µm
F I G . 11. SEM image of the distal part of a spikelet in Scirpus falsus, showing
an initially spiral organization, becoming distichous at later (distally situated)
stages. The red dotted line indicates the rachilla.
image (Fig. 12) shows a cross-section through a spikelet of
Cyperus laevigatus at the height of the insertion of the staminal filaments on the flower receptacle of a flower corresponding to the ‘red’ flower in the SEM image, as indicated by a red
line on the SEM image. In the LM image, the corresponding
flower is encircled. The wings of the flower subtending the
glume (coloured in red) are fused with the rachilla (green
coloured zone). The fusion zone of wings and rachilla grows
with the rising rachilla, as in, for example, Pycreus pumilus
(Fig. 13), consequently lifting up the main part of the
glume. Simultaneously, there is metatopic displacement (see
also the first paragraph in the discussion and Fig. 20) of the
proximal flower primordium, which was raised by the
growth of the rachilla and consequently separated from its subtending glume (indicated by a green double arrow at the righthand image). The developing proximal flower is partially
enclosed by the wings of the subtending glume of the alternate,
higher positioned, second flower. In Pycreus pumilus, the
glume-like prophyll has a swelling body situated between the
prophyll/rachilla and the (removed) rachis. Quite early in
Page 8 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
B
200 µm
500 µm
A
G
F
Rl
F I G . 12. Spikelet structure in Cyperus laevigatus. (A) SEM image of a developing part of a spikelet, with lateral– abaxial view on the flower coloured in red. Of
this flower, the three stamens are visible with the two stigma branches protruding above them. This flower is partially enveloped by the glume wings of the
alternate, upper flower (coloured in blue). Arrows indicate the wing tips. The red line at the base of the flower indicates the zone represented in the transverse
section shown in B, particularly the flower coloured in red. (B) LM image of a transverse section at the base of a flower (encircled in red). The glume of this flower
(coloured in red) has wings which are fused with the rachilla (fusion zone coloured in green). The arrows indicate the wing tips at the alternate side.
Abbreviations: F, flower; G, glume; Rl, rachilla.
100 µm
50 µm
*
Fp
G
Gp
P
F
B
G
F I G . 13. SEM images of a developing spikelet in Pycreus pumilus. The distal part with the rachilla apex is shown at the left; the proximal part with the spikelet
subtending bract is shown at the right. Blue arrows indicate the wing tips of an alternate, more distally situated flower, partially enveloping the given flower. White
arrows indicate the formation of a mucro, which gives the more mature glumes a cap-like aspect. The red arrow indicates the swelling body at the base of the
spikelet prophyll. The double arrow in green shows the metatopic displacement by concaulescent growth of the proximal flower with the rachilla, separating the
flower from the proximal glume. Abbreviations: B, spikelet subtending bract; F, flower; Fp, proximal flower; G, glume; Gp, proximal glume; asterisk (*), rachilla
apex.
their development, the glumes develop a pointed cap-like
mucro (Fig. 13). In Schoenus nigricans, the concaulescent displacement of the distalmost positioned flower is so extreme
that the distal (empty) glume (Gd) is positioned lower than
the distalmost positioned flower (F1). The glume of this distalmost positioned flower (G1), which is not the distal glume, is
positioned alternately and lower than the distal glume
(Fig. 14). In this example the rachilla apex is hidden
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
between the distalmost flower primordium and the distal
glume.
In all Cariceae investigated, the male reproduction units
together form a (co)florescence or terminal spikelet. Each primordium of a male reproduction unit is formed in the axil of a
glume-like scale. These originate successively, immediately
below the apex of the indeterminate rachis. Subsequently,
this primordium differentiates into three stamen primordia.
These develop into filaments and anthers (Fig. 15).
Proximally on the rachis, female, single-flowered spikelets
are formed with a more or less developed rachilla, depending
on the genus or species considered. In most cases, the rachilla
*
F1
Gd
50 µm
G1
F I G . 14. SEM image of the distal part of a spikelet in Schoenus nigricans.
The rachilla apex is hidden between the distal glume, which is the most
recently formed and (still) empty glume, and the most recently formed
flower primordium (F1). This flower primordium is separated from its glume
(G1, which is the second youngest glume after the distal one) by concaulescent
growth with the rachilla (green double arrow), and partially enveloped by the
wings of the distal glume. Abbreviations: F1, most recently formed flower primordium; G1, glume subtending F1; Gd, distal glume; asterisk (*), rachilla
apex.
Page 9 of 17
of a female spikelet grows out radially with respect to the relative main axis. In most Carex species, the rachilla remains
under-developed, only visible at the abaxial side inside the
perigynium ( prophyll), below the female flower, at early
developmental stages as shown here in Carex pendula
(Fig. 16). The prophyll of the spikelet in Carex pendula is
tubular at its base, but forms a two-keeled glume-like structure
at the adaxial side (between rachilla and rachis). The developing, single, female flower of the spikelet is subtended by the
prophyll ( perigynium), and consists of only a dimerous gynoecium with two, laterally situated, stigma primordia. At this
developmental stage, the ovary is still open, showing a
single, centrally positioned ovule primordium (Fig. 16). In
contrast, in Uncina rubra, the prophyll develops very soon
into a closed, tubular utriculus, surrounding both the female
flower it subtends and the rachilla. The rachilla grows out
and a single glume is formed, which because of its position
can be considered to be proximal as well as distal glume.
The female spikelets show torsion with respect to the radial
plane (determined by the rachis and the bract subtending the
spikelet). As a result, the female spikelet appears to be fixed
adjacently on the rachis (Fig. 16). The developing female
flower in Uncinia rubra consists of a trimerous gynoecium,
with the ovary wall surrounding the central ovule primordium,
and on the top of the ovary wall two lateral and a single
abaxial (with respect to the rachilla) stigma primordia
(Fig. 16).
Spikelet reduction has been observed in many other taxa, for
example Lipocarpha. In Lipocarpha nana, an inflorescence at
early developmental stage consists of a indeterminate rachis,
and many, spirally arranged spikelet primordia, each subtended by a bract. This inflorescence primordium is reminiscent of a developing spikelet in Fuirena ciliaris, consisting
of an indeterminate rachilla, and many spirally arranged
glumes, each subtending a flower primordium (Fig. 17).
Spikelet primordia in Lipocarpha nana develop into singleflowered spikelets, each with a prophyll and a proximal
glume, which subtends the flower primordium (Fig. 18).
DISCUSSION
Spikelets are indeterminate ultimate branches of the inflorescence
*
50 µm
F I G . 15. SEM image of the distal part of a spike of spikelets in Carex cristatella, with apical view on the developing terminal male spikelet with several
new glume-like bracts, each subtending a male flower primordium at different
stages of development (yellow, newly originating bract; green, bract with
undifferentiated flower primordium; blue, bract with flower primordium differentiating into three stamen primordia). Abbreviation: asterisk (*), rachis apex.
In most of the species studied, lateral spikelets obviously
consist of an indeterminate rachilla, few to many lateral, distichously to spirally arranged glumes, each subtending (or not) a
flower, and a prophyll at the base of the rachilla. All terminal
spikelets observed also have an indeterminate axis. In all spikelets studied, older flowers are always situated proximally,
whereas new glumes always appear laterally, immediately
beneath the rachilla (or axis) apex. Therefore, each previous
attempt to interpret spikelets as sympodial structures (e.g.
Celakovsky, 1887; Kern, 1962; Richards et al., 2006) seems
artificial and requires several auxiliary hypotheses to support
the interpretation (Vrijdaghs et al., 2007). However, it is
clear that some spikelets are more complex and difficult to
interpret. Distichously arranged spikelets with winged
glumes in particular have caused interpretational confusion.
These spikelets were used as an argument in favour of the sympodial interpretation. Therefore, much attention was given to
Page 10 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
*
o
50 µm
sg
sg
20 µm
Gp
*
Rl
sg
o
ov
sg
sg
P
Rl
*
B
P
B
F I G . 16. SEM images of female spikelets in Carex pendula (left) and Uncinia rubra (right). The view on the female flower in C. pendula is adaxial with respect
to the rachilla or abaxial if the rachis (not visible) is taken as reference, with the rudimentary rachilla below the female flower. The developing prophyll (perigynium) is situated between rachilla and rachis, at this developmental stage forming two conspicuous keels. The developing female flower consists of a dorsiventrally flattened ovary. The still open ovary wall surrounds the central ovule. On the top of the ovary wall, two laterally situated stigma primordia are visible. The
female spikelets in U. rubra underwent a torsion with respect to the plane defined by the rachis and the bract subtending the considered spikelet, so that they
appear adjacently positioned. The image gives an abaxial (with respect to the rachilla) view of the female flower, subtended by the tubular spikelet prophyll,
which forms a nearly closed perigynium. The rachilla in U. rubra grows out and a first glume or proximal glume is formed. This glume can also be termed
distal glume, as no other glumes are formed. Abbreviations: B, bract subtending a spikelet; Gp, proximal glume; o, ovule; ov, ovary wall; Rl, rachilla; sg,
stigma primordium; P, spikelet prophyll; asterisk (*), rachilla apex.
distichously organized spikelets with glumes with large wings,
such as the spikelets in many species of the Cypereae tribe
(sensu Goetghebeur, 1998). Vrijdaghs et al. (2007) showed
that spikelets in Schoenus nigricans have the same Bauplan
(building plan, blueprint) as the spikelets in most other cyperoid genera. They considered the interpretational confusion in
spikelets in Schoenus nigricans to be caused by concaulescent
metatopic displacement (Weberling, 1992) of flowers. This
causes the distal glume to be positioned lower than the last
formed flower. The glumes in Schoenus nigricans are
winged, with the wings partially enveloping the lower alternate
flower. This is also the case in most Cypereae species.
Figures 12 and 13 show that the bases of the wings are
fused with the rachilla. This fusion zone grows with the
rising rachilla, elongating the wing tips along the internode
and displacing the main part of the glume and the flower primordium in its axil.
In summary, the idiosyncratic structure of distichously organized spikelets is due to two distinct phenomena of metatopic
displacement which may be present simultaneously to a
greater or lesser degree: (1) concaulescent growth of the
flower with the rachilla, which separates it from its subtending
glume; and (2) in distichously organized spikelets most of a
glume (including the flower primordium in its axil) is displaced
by the growth of the fusion zone of the rachilla itself (and not a
newly formed lateral axis) and the wings of the glume. As a
consequence, a glume originates at a node, and subsequently
the main part of it is raised to a higher level, the next node on
the rachilla. Hence, the fusion zone of the wings of a glume
and rachilla runs along the internode. At the initial insertion
point of the glume, the wing tips may develop, partially enveloping a previously formed flower, which is at a lower position
of the alternate side with respect to the displaced main part of
the considered glume (Figs 12, 13 and 19). This kind of metatopic displacement was not defined by Weberling (1992), who
distinguished between concaulescence, recaulescence and anaphysis: ‘In recaulescence the axillary bud is shifted for some
distance towards the base of the subtending leaf, the insertion
of which is displaced on the branch for a smaller or greater
distance above its original position, after stretching of the
common basal zone of both organs’ (Weberling, 1992,
p. 217). Consequently, in recaulescence, the main part of a
bract is displaced by growth of the newly formed lateral axis
which it subtends, thus transforming the part of the newly
formed axis between the insertion point of the bract (where
the new axis initially originated) and the displaced main part
of the bract into a recaulescent zone. The lateral axis develops
further above the displaced main part of the bract, there consisting of a ‘normal’ axis which will be terminated by a flower
(Fig. 20). The metatopic displacement of the main part of the
glumes in distichous spikelets also differs from Weberling’s
definition of anaphysis: ‘We speak of anaphysis if an axillary
bud with its subtending bract “is moved up to a position
above the bract which follows it genetically” . . . ’ (Weberling,
1992, p. 218).
Therefore, we suggest a new term for this kind of ‘recaulescence along the rachilla itself’, epicaulescence, as the displacement of the main part of the glume occurs upon the
rachilla (Figs 19 and 20). In Schoenus nigricans, the concaulescent metatopic displacement of the flower is quite
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
extreme, so it is possible that the next glume originates
between the newest flower, which seems to be positioned
above the rachilla apex and its subtending glume (Fig. 14).
As a consequence, this phenomenon, combined with the epicaulescent growth of the wings of the glumes, gives the
impression that the flower is terminating a new lateral axis.
In spikelets of Cyperus falsus, the proximal glumes are
arranged spirally, whereas the distal ones are arranged distichously. Consequently, distichous arrangement of the glumes
occurs at later stages of spikelet development. However, in
Abildgaardia, the proximal glumes are arranged distichously
and the distal ones spirally. In some species, such as Ficinia
fascicularis, Machaerina anceps and Rhynchospora pubera
(Goetghebeur, 1986), co(florescences) or terminal spikelets
have a spiral arrangement of the glumes, whereas the lateral
spikelets have a distichous organization. In contrast, in
Blysmus the terminal spikelets are distichously organized and
the lateral ones spirally. This shows that the characters ‘distichous/spiral (and all intermediary phyllotaxies) arrangement
of the glumes’ often depend on conditions of growth and
spacial environment.
*
1
Sp
2
B
50 µm
3
Page 11 of 17
2
3
F
G
Female spikelets and male (co)florescences/terminal
spikelets in Cariceae
*
1
4
50 µm
F I G . 17. SEM images of the distal part of a spike of spikelets in Lipocarpha
nana (top) compared with the distal part of a spikelet in Fuirena ciliaris
(bottom). Arrows indicate bracts subtending a spikelet, each with a spikelet
primordium in its axil for L. nana, and glumes, each with a flower primordium
for F. ciliaris. Numbering from young (1) to more mature. Abbreviations: B,
bract; F, flower primordium; G, glume; Sp, spikelet primordium; asterisk
(*), rachis/rachilla apex.
*
100 µm
F I G . 18. SEM image; apical view of the distal part of a spike of spikelets in
Lipocarpha nana. Encircled in red is a developing, single-flowered spikelet.
Red arrows indicate spikelet prophylls, yellow arrows glumes subtending a
flower. Abbreviation: asterisk (*), rachis apex.
In Cariceae, the inflorescence is often a spike of spikelets with
the male reproductive units at the distal part, and the female spikelets proximally (Figs 9, 15 and 21). Ontogenetically, this
Bauplan or building plan raises questions about the concept of
the spikelet itself, as Timonen (1998) has already stated.
Moreover, as the male reproductive units as well as the female
spikelets each originate from a primordium in the axil of a
bract, all these primordia are (serially) homologous, taking positional homology as the main criterion (Fig. 21; Remane, 1956;
Classen-Bockhoff, 2005). This logically brought Timonen to
suppose that the male reproductive units must be highly
reduced male spikelets (Timonen, 1993, 1998). However,
neither she nor other investigators found indications of a
reduction of a hypothetical more developed spikelet with male
flowers. In contrast, in the female spikelets, such reduction
series exists (e.g. Haines and Lye, 1983; Goetghebeur, 1986).
Moreover, ontogenetic investigation of the male reproductive
units has until now not revealed remnants of spikelet structures
such as a prophyll, rachilla, glumes or non-androecial floral
parts (Fig. 15). Therefore, we consider that the male reproduction units are not derived by reduction from a hypothetical ancestral spikelet and that, consequently, further ontogenetic research
for remnants of such a reduction is of little value. We consider
the male reproductive units to be real male flowers. In analogy
with Gould’s (2002) suggestion that floral primordia or phyllomes can be considered as ‘empty boxes’ to be filled in by
the expression of developmental processes and regulation
systems such as the ABC-model of Weigel and Meyerowitz
(1994), we postulate that all primordia formed in the axil of successively originating glumes/bracts should be considered as
developmentally undetermined, homologous by position to
each other and consequently serial homologues. However,
due to the open nature of plant development, primordia have
a large flexibility to follow one (or possibly several
simultaneously expressed) developmental programme(s). The
Page 12 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
A
*
G1 F1
A
F2
G2
Recaulescent growth (after Weberling, 1992)
B
B
Epicaulescent growth in distichously organized spikelets
G1 F1
*
F2
C
G2
C
Concaulescent growth (after Weberling, 1992)
G1
F1
F2
G2
F I G . 19. Schematic outline of the structure of a distichously organized spikelet, based on empirical observation. (A) Lateral view of the distal part of the
rachilla. (B) Transverse section as indicated by a line in (A). (C) Lateral
view on an internode of a spikelet. Arrows indicate the growth direction of
the rachilla. Numbers from young (1) to old (2). In (A), G1 corresponds to
the distal glume, subtending the distal flower F1. Shaded zones represent
fusion zones between wings of glumes and the rachilla. Because of epicaulescent growth of these zones with the rachilla, the wings of the glumes are
elongated along the alternate side of the rachilla. They envelop partially a
lower, alternate flower. Abbreviations: F, flower; G, glume; asterisk (*),
rachilla apex.
activated developmental programme(s) will eventually determine the ‘special quality’ (Remane, 1956) of the structure that
is developed from a given primordium; in other words, its identity. Because of the flexibility of plants to activate different
developmental programmes in a given primordium according
F I G . 20. Schematic theoretical outline of different kinds of metatopic displacement: concaulescence and recaulescence after Weberling (1992); epicaulescence, a newly defined metatopic displacement based on our empirical
observations in distichously organized cyperoid spikelets. Concaulescent
growth of a flower primordium occurs when it is partially fused with the
rachilla apex and lifted up by the growth of the rachilla. Consequently, the
flower primordium is separated from its glume. Recaulescence occurs when
a similar partial fusion of a bract primordium with the axis it subtends
causes part of the developing bract to be lifted up by the growth of the
lateral axis. Epicaulescence differs from recaulescence in the fusion of a
part of the distal bract primordium with the apex of the rachilla. When the
rachilla grows, the bract is partially shifted upwards along the rachilla. Both
recaulescence and epicaulence usually cause the axis where the respective
phenomenon occurs to be winged.
to circumstances and needs of the moment, we consider that in
plants, ‘special quality’ is a secondary, though indispensable,
homology criterion, as it depends on the activation of the developmental programme(s) that will eventually give identity to the
structure; the only stable morphological homology criterion
referring to the ontogenetic origin is ‘position’ (Remane,
1956; Classen-Bockhoff, 2005). This explains that in
Cariceae, homologous primordia can develop into structures
as different as female spikelets and male flowers. The abovementioned developmental flexibility of plants also explains
why we do not find remnants of spikelet structures in the male
flowers, as the switching on or off of developmental programmes
(in the case of Cariceae, it concerns the programmes making a
given primordium develop into a male flower, or a female spikelet) is not the result of evolution. The fact that in Cariceae this
kind of inflorescence apparently is successful only shows that
using flexibility in the ‘filling in of empty boxes’ can result in
fit plants. Moreover, in Cariceae, the female spikelets are deciduous as a whole. In contrast, the male reproductive units are not,
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
homologous with
100 µm
*
Page 13 of 17
?
F I G . 21. SEM images of a spike in Uncinia rubra, showing the development of a primordium (red frame) into either a male reproduction unit (yellow frame)
situated in the florescence, or a female spikelet (blue frame). The latter occurs only at very early stages of spike development, and consequently later female
spikelets are always situated proximally in the spike.
and these usually terminate a culm or a lateral axis (with the
exception of Carex section Vignea). Consequently, male
(co)florescences are considered to be terminal spikelets, consisting of the axis and glumes subtending male flowers.
Symptoms of an ontogenetic switch ‘flower/lateral spikelet’
In several species of the tribe Cypereae sensu Goetghebeur
(1998), a highly derived tribe within Cyperoideae (Fig. 1), a
similar, but inverse phenomenon within spikelets was
observed: primordia in the axil of new glumes are supposed
to develop into flowers. However, often some of these primordia do not develop into a flower, but into a secondary spikelet
(Vrijdaghs et al., 2009). Here, too, all primordia in the axil of a
glume are position homologues. And the ‘filling in of the
empty box’ determines the final ‘special quality’ of the resulting structure, ‘flower’ or ‘secondary spikelet’. One might interpret (as we earlier did) this phenomenon as an indication that
spikelets result from a reduction of a compound partial inflorescence, but why then have we not found more transitional
forms in all tribes, especially the more basal ones such as
Scirpeae (Fig. 1)? The answer is again that there was no
such evolution from a compound partial inflorescence to a
modern spikelet, but that the occurrence of secondary spikelets
follows from the flexibility that plants possess to activate
different developmental programmes in a given primordium.
Related to the discussion above about the determination of a
given primordium is the study of the transition zone in
species with terminal spikelets, such as Cyperus luzulae.
Following Weberling (1992), a terminal spikelet is a florescence (Guarise and Vegetti, 2008), with bracts (glumes)
each subtending a flower. These originate in the same way as
in lateral spikelets, immediately beneath the apex of the axis
(rachis). Developing bracts soon get a primordium in their
axil, which develops into a flower, or at a given moment
into a spikelet. Again this concerns position homologues,
empty boxes, which will be filled in first as spikelets and
later as flowers. Another illustration of this principle is given
by the development of species of Lipocarpha. There is a striking analogy between the development of an inflorescence
(spike of spikelets) of a species such as Lipocarpha nana
and the development of a spikelet in one such as Fuirena
ciliaris (Figs 17 and 18). However, each primordium in
L. nana is determined to develop into a single flower spikelet,
whereas similar primordia in F. ciliaris develop into flowers
(Fig. 18). The results of Smith (1967), showing that phytohormones influence the determination of axillary primordia in
Carex (whether they develop into male flower, lateral spike
of spikelets or female spikelets), also suggest the existence
of an ontogenetic switch.
CO NC L US IO NS
In all cyperoid species studied, spikelets, the ultimate inflorescence branches, consist of a indeterminate rachilla, and one to
many spirally to distichously arranged glumes, each subtending (or not) a flower. Typologically, spikelets are open
spikes or racemose ultimate inflorescence branches. In spikelets with distichously arranged glumes, the glumes often
have wings. A fusion zone of the wings of a glume and the
rachilla grows out with the rising rachilla, displacing metatopically the main part of the glume and the flower primordium in
its axil to the next node. This previously undescribed kind of
metatopic displacement is termed here ‘epicaulescence’.
Moreover, in distichously organized spikelets, the flowers
tend to grow concaulescently with the rachilla, which separates
them from their subtending glume. The combination of both
metatopic displacement phenomena results in a zigzagging
Page 14 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
rachilla at maturity, which caused interpretational controversy
in the past. In several clades, particularly the most derived
ones, there is a tendency towards reduction of the spikelets
and to transfer the spikelet functions to the inflorescence. In
Cypereae, primordia in the axil of a glume sometimes
develop into a secondary spikelet instead of a flower. This
can be explained by a putative ontogenetic switch which determines whether such a primordium will develop into a flower or
into a lateral axis (secondary spikelet). In that way, in
Cariceae, the initial formation of (later in the development
of the proximally positioned spike) female single-flowered spikelets and later the formation of (consequently distally positioned) male flowers, both from positionally homologous
primordia, can be understood.
AC KN OW LED GEMEN T S
We thank Jeremy Bruhl (University of New England, NSW,
Australia) and Regine Classen-Bockhoff (Gutenberg
University, Mainz, Germany) for their theoretical contributions to spikelet structure and morphological homology
respectively, and also our laboratory technicians Anja
Vandeperre (schemes) and Nathalie Geerts (LM). This work
was supported financially by research grants of the K.U.
Leuven (OT/05/35) and of the Fund for Scientific
Research-Flanders (FWO-Vlaanderen, Belgium, G.0268.04).
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Page 15 of 17
APP E ND IX 1
Species of Cyperaceae studied and voucher data
Species
Alinula lipocarhoides
Baumea rubiginosa
Bulbostylis hispidula
Bulbostylis hispidula
Carex capitata
Carex capitata
Carex cristatella
Carex elata
Carex pallescens
Carex pendula
Carpha sp.
Cladium mariscus
Cladium mariscus
Cladium mariscus
Coleochloa setifera
Courtoisina assimilis
Cyperus capitatus
Cyperus captitatus
Cyperus congestus
Cyperus denudatus
Cyperus digitalis
Cyperus distans
Cyperus distans
Cyperus dubius
Cyperus dubius
Cyperus eragrostis
Cyperus haspan
Cyperus hemisphaeriscus
Cyperus involucratus
Cyperus kerstenii
Cyperus laevigatus
Cyperus laevigatus 2002 0878
Cyperus laevigatus
Cyperus luzulae
Cyperus pectinatus
Cyperus podocarpus
Cyperus prolifer
Cyperus natalensis
Cyperus owanii
Cyperus pulchellus
Cyperus rotundus
Cyperus rotundus
Cyperus squamosus
Scirpus falsus
Dulichium arundinaceum
Eleocharis palustris
Eleocharis palustris
Eriophorum latifolium
Eriophorum latifolium
Ficinia angustifolia
Ficinia brevifolia
Ficinia bulbosa
Ficinia capitella
Ficinia distans
Ficinia dunensis
Ficinia gracilis
Ficinia gracilis
Ficinia minutiflora
Ficinia minutiflora
Ficinia nigrescens
Ficinia polystachya
Ficinia radiata
Ficinia scandia
Collected by
Muasya
Hodgon/Bruhl
Muasya
Muasya
Goetghebeur
Goetghebeur
AV
AV
AV
Goetghebeur
Muasya
AV
AV
AV
Muasya
Muasya
Goetghebeur
Reynders
Reynders
Muasya
Muasya
Mwachala
Muaysa
Muasya
Mwachala ea
I. Larridon
Muasya
Mwachala ea
I. Larridon
Muasya
Goetghebeur
Reynders
Muasya
AV
Mwachala
A Chevalier
I. Larridon
Muasya
I.Larridon
Muasya
Muasya
Muasya
Muasya
Muasya
Goetghebeur
AV
AV
Goetghebeur
AV
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Esterhuysen
Muasya
Muasya
Muasya
Muaysa
Muasya
Localization
Kenya
Western Australia
Kenya
Kenya
University of Gent
University of Gent
University of Gent
Ptk-K.U. Leuven
Ptk-K.U. Leuven
University of Gent
South Africa (SA)
KDTN-Leuven
KDTN-Leuven
NPMeise
Kenya
Kenya
University of Gent, HBUG2003-1782(w)
University of Gent, HBUG2003-1782(w)
University of Gent, HBUG2002-0872
Kenya
Kenya
SA
Kenya
Kenya
Kenya
University of Gent, HBUG1986-0588
Kenya
Kenya
University of Gent, HBUG1900-1130
Kenya
University of Gent, HBUG1997-1237
University of Gent, HBUG2002-0878
Kenya
University of Gent (S.Am), HBUG1900-3306
Kenya
Mali
University of Gent, HBUG2001-1697
SA
University of Gent, HBUG1985-0260
Kenya
Kenya
Kenya
Kenya
SA
University of Gent
KDTN-Leuven
KDTN-Leuven
University of Gent
KDTN-Leuven
Cape Peninsula, SA
Cape Peninsula, SA
Calendon, SA
Cape Peninsula, SA
Calendon, SA
Calendon, SA
Swellendam, SA
Kenya
Calendon, SA
Calendon, SA
SA
Cape Peninsula, SA
Calendon, SA
SA
Date
10/2003
04/2005
04/2005
05/2005
04/2002
04/2001
12/2006
04–06/2002
04–06/2002
05/2002
12/2006
2008
2008
2005
09/2004
2006
1910
2008
04/2008
2008
04/2008
2003
09/04/02
03/2004
07/11/2002
07/11/2002
15/11/2002
07/11/2002
21/11/2002
15/11/2002
16/11/2002
1975
17/11/2002
12/2006
30/11/2002
17/11/2002
12/2006
Voucher number
AM 2592
JH 792
AM 2126
AM 2466
PG 10465
PG 10466
AV 11
AV 07
AM 2907
AV 05
AV 05
AV 06
AM 2464
AM 2124
PG 10744
2002-0872
AM 2417
AM 2162
Mwachala 694
AM 2121
AM 2188
EW 3878
1986-0588
AM 2135 (EA)
EW 3893
1900-1130
AM 2534
PG 10202
2002-0878
AM 2610
19003306
Mwachala 341
AC 2472 (BR)
2001-1697
AM 3805
1985-0260
AM 2131
AM 2117
AM 2164
AM 2122
AM 3748
PG 9914
AV07a
AV07b
PG 10185
AV 04
AM 2202
AM 2205 (BOL, EA, K)
AM 2243
AM 2206 (BOL, EA, K)
AM 2283
AM 2242
AM 2248 (BOL, EA, K)
AM 2571
33777 (PRE)
AM 2257 (BOL, EA, K)
AM 2881
AM 2320
AM 2262 (BOL, EA, K)
AM 2908
Continued
Page 16 of 17
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
APPENDIX 1 Continued
Species
Ficinia tristachya
Ficinia tristachya
Ficinia zeyheri
Fimbristylis complicata
Fimbristylis dichotoma
Fimbristylis ferruginea
Fimbristylis pterigosperma
Fimbristylis tetragona
Fimbristylis xyridis
Fuirena abnormalis
Fuirena ciliaris
Fuirena leptostachya
Fuirena pubescens
Hellmuthia membranacea
Hellmuthia membranacea
Isolepis antarctica
Isolepis digitata
Isolepis fluitans
Isolepis fluitans
Isolepis prolifera
Isolepis setacea
Isolepis setacea
Isolepis setacea
Kobresia myosaroides
Kobresia myosaroides
Kyllinga eximia
Kyllinga apendiculata
Kyllinga bulbosa
Kyllinga chlorotropis
Kyllinga comosipes
Kyllinga comosipes
Kyllinga flava
Kyllinga flava
Kyllinga microbulbosa
Kyllinga microbulbosa
Kyllinga monocephala
Kyllinga nemoralis
Kyllinga polyphylla
Kyllinga vaginata
Kyllingiella polyphylla
Kyllingiella polyphylla
Lepidosperma tetraquetrum
Lipocarpha chinensis
Lipocarpha isolepis
Lipocarpha leymannii
Lipocarpha nana
Oxycaryum cubense
Pseudoschoenus sp.
Pycreus bipartitus
Pycreus flavescens
Pycreus pelophylus
Pycreus pelophilus
Pycreus podophylla
Pycreus polystachyos spp. holosericeus
Pycreus pumilus
Pycreus sanguinolentus
Pycreus sanguinolentus
Queenslandiella hyalina
Queenslandiella hyalina
Rhynchospora DO150138
Rhynchospora cephalotes
Rhynchospora nervosa
Schoenoplectus senegalensis
Schoenoxiphium leymanii
Schoenoxiphium sparteum
Schoenus melanostachys
Collected by
Muasya
Muasya
Muasya
Muasya
Malombe&AMM
Muasya
Harwood
Harwood
Harwood
Muasya
Harwood
Muasya
Muasya
Bytebier
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Muasya
Goetghebeur
Reynders
Muasya
Muasya
Reynders
Muasya
Musili
Muasya
Muasya
Musili
Muasya
Mwachala
Reynders
M. Reynders
Reynders
Caris
Muasya
Muasya
Hodgon/Bruhl
Mwachala
Muaysa
Muasya
Muasya
Mwachala ea
Muasya
Reynders
Reynders
Muasya
Musili
Muasya
Reynders
Muasya
Muasya
Reynders
Muasya
Muasya
Harwood
MS Samain
Reynders
Malombe-Muasya
Malombe
Muasya
Bruhl
Localization
Calendon, SA
Calendon, SA
Calendon, SA
Kenya
Kenya
Kenya
Australia, Northern Territories (NT)
Australia, NT
Australia, NT
Kenya
Australia NT
Kenya
Kenya
Cape Peninsula, SA
Cape Peninsula, SA
Swellendam, SA
Calendon, SA
Kenya
Kenya
Calendon, SA
Kenya
Kenya
SA
University of Gent
University of Gent, HBUG3003-0642
Kenya
Kenya (alpine zone)
University of Gent
Kenya
Kenya
Kenya
Kenya
Kenya
Kenya
SA
University of Gent
University of Gent, HBUG2006-1237
Kenya
Berlin, Germany
Kenya
Kenya
Western Australia
SA
Kenya
Kenya
Kenya
Kenya
SA
University of Gent, HBUG2005-0801(s)
University of Gent, HBUG2005-0401
Kenya
Kenya
Kenya
University of Gent, HBUG2006-1258(w)
Kenya
Kenya
University of Gent, HBUG2006-1753 (w)
Mombasa (Kenya)
Mombasa (Kenya)
Australia (NT)
Surinam
Philipines/HBUG2002-0277
Kenya
Kenya
Kenya
North-east Australia
Date
Voucher number
17/11/2002
17/11/2002
17/11/2002
AM 2255
AM 2256
AM 2209 (BOL, EA, K)
AM 2147
Malombe 41
AM 2127
RKH 1163
RKH 1128
RKH 1162
AM 2192
RKH 1173
AM 2136
AM 2149
Bytebier 2645
AM 2792
AM 2247 (BOL, EA, K)
AM 2258
AM 2604
AM 2541
AM 2265
AM 2558 (EA)
AM 2547
AM 2540
PG 10009
3003-0642
AM 2137
AM 2563
31/07/05
07/2005
16/11/2002
17/11/2002
2005
2005
17/11/2002
2005
12/2006
2004
2006
2005
12/2004
2005
2005
2005
2005
12/2006
2008
12/2004
02/2002
03/10/2003
12/2006
12/2006
12/2006
12/2006
11/2004
2008
2005
2005
07/07
2005
07/07
08/2006
11/2007
2005
2007
AM 2606
MM 001
AM 2119
AM 2125
MM 009
AM 2658
Mwachala 799
MR 19
2006-1237
AM 2123
AM 2435
JH 737
Mwachala 873
AM 2748
AM 3132
AM 2194
Mwachala 340
AM 3061
2005-0401
AM 2139
MM 029
AM 2139
2006-1258
AM 2134
AM 2157
2006-1753
AM 2189
AM 2190
RKH 1127
MS2006 018
2002-0277
Malombe 40
KG96
AM 2566
J.J. Bruhl 2447 (NE)
Continued
Vrijdaghs et al. — Spikelet structure and development in Cyperoideae
Page 17 of 17
APPENDIX 1 Continued
Species
Schoenus nigricans
Scirpoides holoschoenus
Scirpus sylvaticus
Scleria rugosa
Uncinia divaricata
Uncinia divaricata
Uncinia rubra
Collected by
AV
AV
AV
Harwood
Goetghebeur
Goetghebeur
Goetghebeur
Localization
Ptk-K.U. Leuven
KDTN-Leuven
Ptk-K.U. Leuven
Australia (NT)
University of Gent/New Zealand
University of Gent
University of Gent
Date
04/2003
10/2001
10/2001
09/2001
Voucher number
AV 01
AV 03
AV02
RKH 1134
1998-07771-W
PG 9728
PG 9727
Abbreviations: AV, A. Vrijdaghs; KDTN-Leuven, botanical garden of the town of Leuven, Belgium; Ptk-K. U. Leuven, botanical garden of the Institute of
Botany of the K. U. Leuven, Belgium; University of Gent, botanical garden of the University of Ghent, Belgium.
APPENDIX 2
Authorities of cyperoid species and genera mentioned
in the text.
Abildgaardia Vahl
Ascolepis Nees ex Steudel
Carex L.
Carex cristatella Britton
Carex pendula Moench.
Cyperus L.
Cyperus alternifolius L.
Cyperus capitatus Poir.
Cyperus congestus Vahl
Cyperus haspan L.
Cyperus laevigatus L.
Cyperus luzulae Rottb. ex Willd.
Dulichium L.C. Richard
Dulichium arundinaceum (L.) Britton
Eleocharis palustris (L.) Roem. & Schult.
Eriophorum latifolium Hoppe
Ficinia brevifolia Nees ex Kunth
Ficinia fascicularis Nees
Fuirena ciliaris (L.) Roxb.
Kyllinga Rottb
Lipocarpha R. Brown
Lipocarpha chinensis Osb.
Lipocarpha nana (A.Rich.) Cherm.
Machaerina anceps (Poir.) Bojer
Mariscus Vahl
Pycreus P.Beauv.
Pycreus polystachyos (Rottb.) P.Beauv.
Pycreus pelophilus (Ridl.) C.B.Clarke
Pycreus pumilus (L.) Nees
Pycreus sanguinolentus Nees
Queenslandiella Domin
Rhynchospora latifolia (Baldwin ex Elliott) W.W.Thomas
Rhynchospora pubera Boeckeler
Schoenus nigricans L.
Scirpoides holoschoenus (L.) Sojàk
Scirpus falsus C.B. Clarke
Scirpus sylvaticus L.
Torulinium Desv.(¼Cyperus)
Uncinia Pers.
Uncinia rubra Colenso ex Boott