Content uploaded by Peter K Endress
Author content
All content in this area was uploaded by Peter K Endress on Aug 28, 2014
Content may be subject to copyright.
Floral structure of Emmotum (Icacinaceae sensu stricto or Emmotaceae), a
phylogenetically isolated genus of lamiids with a unique pseudotrimerous
gynoecium, bitegmic ovules and monosporangiate thecae
Peter K. Endress1,* and Alessandro Rapini2
1
Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland and
2
Departamento de
Cie
ˆncias Biologicas, Universidade Estadual de Feira de Santana, Av. Universita
´ria s/n, CEP 44036-900, Feira de Santana,
Bahia, Brazil
* For correspondence. E-mail pendress@systbot.uzh.ch
Received: 23 May 2014 Returned for revision: 13 June 2014 Accepted: 30 June 2014
†Background and Aims Icacinaceae sensu stricto consist of a group of early branching lineages of lamiids whose
relationships are not yet resolved and whose detailed floral morphology is poorly known. The most bizarre flowers
occur in Emmotum: the gynoecium has three locules on one side and none on the other. It has been interpreted as
consisting of three fertile and two sterile carpels or of one fertile carpel with two longitudinal septa and two
sterile carpels. This study focused primarily on the outer and inner morphology of the gynoecium to resolve its dis-
puted structure, and ovule structure was also studied. In addition, the perianth and androecium were investigated.
†Methods Flowers and floral buds of two Emmotum species, E. harleyi and E. nitens, were collected and fixed in the
field, and then studied by scanning electron microscopy. Microtome section series were used to reconstruct their
morphology.
†Key Results The gynoecium in Emmotum was confirmed as pentamerous, consistingof three fertile and two sterile
carpels. Each of the three locules behavesas the single locule in other Icacinaceae, with the placenta of the two ovules
being identical, which shows that three fertile carpels are present. In addition, it was found that the ovules are biteg-
mic, which is almost unique in lamiids, and that the stamens have monosporangiate thecae, which also occurs in the
closely related family Oncothecaceae, but is not known from any other Icacinaceae sensu lato so far.
†Conclusions The flowers of Emmotum have unique characters at differentevolutionary levels: the pseudotrimerous
gynoecium at angiosperm level, the bitegmic ovules at lamiid level and the monosporangiate thecae at family or
family group level. However, in general, the floral morphology of Emmotum fits well in Icacinaceae. More compara-
tive research on flower structure is necessary in Icacinaceae and other early branching lineages of lamiids to better
understand the initial evolution of this large lineage of asterids.
Key words: Asterids, Emmotaceae, Emmotum harleyi,E. nitens, Garryales, Icacinaceae, early branching lamiids,
anthers, floral morphology, gynoecium, ovules.
INTRODUCTION
The former family Icacinaceae sensu lato (s.l.) turned out to be
polyphyletic in molecular phylogenetic analyses (Karehed,
2001) and was provisionally subdivided into four distantly
related families: Cardiopteridaceae and Stemonuraceae, both
in Aquifoliales (campanulids), Pennantiaceae in Apiales (cam-
panulids) and Icacinaceae sensu stricto (s.s.), which appear unre-
solved close to the base of lamiids (Karehed, 2001;Lens et al.,
2008;Refulio-Rodriguez and Olmstead, 2014). Metteniusa,
earlier also in Icacinaceae s.l., was placed in a fifth family,
Metteniusaceae, also close to the base of lamiids (Gonza
´lez
et al., 2007), and is here considered to be in Icacinaceae s.s.
as well.
Karehed (2001) recognized Icacinaceae s.s. along with
Garryales s.s. (Aucuba and Garrya) within an expanded
Garryales (s.l.) and divided the family into the ‘Icacina group’
(numerous genera), the ‘Emmotum group’ (Emmotum and
Ottoschulzia) and the ‘Apodytes group’ (Apodytes and
Raphiostylis). Lens et al. (2008), based on combined molecular
and wood anatomical analyses, found very weak support for a
clade consisting of the Apodytes and Emmotum groups plus
Oncotheca and Cassinopsis, whereas Refulio-Rodriguez and
Olmstead (2014), based on combined plastid and mitochondrial
data, found Cassinopsis to be closer to the Icacina group.
In neither of these studies, however, did Icacinaceae s.s. form a
clade.
According to APG III (2009),Apodytes,Cassinopsis and
Emmotum may not even belong to Icacinaceae s.s. and may be
better placed in their own family Emmotaceae (a family pro-
posed earlier just for Emmotum by van Tieghem, 1897), which
might eventually be included in Garryales s.l., probably along
with Metteniusaceae and Oncothecaceae. This ordinal circum-
scription, however, has not been confirmed in more recent phylo-
genetic analyses with molecular data. Whereas Lens et al. (2008)
found the Icacina group closer to core lamiids, Refulio-Rodriguez
and Olmstead (2014) found Garryales s.s. closer to the core
lamiids, in both cases without good support. Figure 1shows a
summary of phylogenetic relationships among Icacinaceae s.l.
and the classification adopted here.
#The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
For Permissions, please email: journals.permissions@oup.com
Annals of Botany Page 1 of 15
doi:10.1093/aob/mcu166, available online at www.aob.oxfordjournals.org
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
The floral structure of Icacinaceae s.l. is in general extremely
rudimentarily known. In contrast to other asterids, the flowers in
this group seem to be less fancy and the high tannin content and/
or woody tissues provide technical difficulties for the production
of serial microtome sections. As a consequence, the floral struc-
ture has not been studied in detail in any of the former Icacinaceae
s.l., except for Cardiopteris (Tobe, 2012;Kong et al., 2014) and
Metteniusa (Gonza
´lez and Rudall, 2010), but in both without
analysis and reconstruction of the inner morphological surface
of the gynoecium. Furthermore, drawings of the small flowers
in revisionary works provide only minimal information (e.g. de
Stefano et al., 2013). None of the taxa of Icacinaceae s.s. has
been studied in detailed floral morphology. Ovary wallhistology
and fruit development have been investigated in Apodytes and
Cassinopsis, but with a focus rather on ecological than on mor-
phological aspects (Potgieter and van Wyk, 1994a,b).
In view of the systematic decomposition and profoundly new
arrangement of the former family Icacinaceae (Fig. 1), it would
be of interest to know more about the detailed floral structure of
the newly established groups. The flowers of Emmotum are dif-
ferent from all other clades of Icacinaceae s.l. because of their
trilocular ovary (Howard, 1942a;Sleumer, 1942), whereas
the ovary is unilocular in Stemonuraceae, Cardiopteridaceae,
Metteniusaceae and the other Icacinaceae s.s. (Sleumer, 1942;
Potgieter and van Wyk, 1994a,b;de Stefano and Ferna
´ndez-
Concha, 2011). In addition, this trilocular ovary of Emmotum
is strangely one-sided in a unique way (Howard, 1942a: plate I,
fig. 9; plate IV, figs 6, 7). Its structure has been variously inter-
preted as pentamerous with two sterile and three fertile carpels
(Engler, 1872;van Tieghem, 1897;Howard, 1942a), or as tri-
merous having two sterile carpels and a single fertile carpel
with two septa (Stevens, 2001 onwards).
Gynoecium and ovule structure are of particular interest for in-
vestigation: the gynoecium because of the mentioned one-
sidedness in Emmotum and the general trend of reduction of
one or more carpels in Icacinaceae s.l., and the ovules because
of reductions of nucellus and integument (Fagerlind, 1945).In
addition, during this study we found an unusual feature of supra-
familial interest in the androecium so that we additionally focus
on stamen structure. We also paid attention to the perianth, which
is characterized in many Icacinaceae s.l. by its valvate petals.
This is the first study on the detailed outer and inner morph-
ology of the highly unusual flowers of an enigmatic genus in
early diverging lamiids. It is to be hoped that currently ongoing
studies on the phylogeny of basal lamiids (Refulio-Rodriguez
and Olmstead, 2014;Stull et al., 2014) and future structural
studies will shed additional new light on the early evolution of
this highly successful group of flowering plants.
MATERIAL AND METHODS
We collected and studied the two species of Emmotum that are
known from the Chapada Diamantina (State of Bahia, Brazil)
(Zappi et al., 2003;de Stefano et al., 2007):
Emmotum harleyi R. Duno (coll. A. Rapini and P.K. Endress
2005, 12 02 2013) (collection locality close to the type local-
ity), floral buds and anthetic flowers.
Emmotum nitens (Benth.) Miers (coll. A. Rapini and P.K.
Endress 2001, 06 02 2013), floral buds.
Other taxa of Icacinaceae s.s. were also studied cursorily for
comparison:
Apodytes brachystylis F. Muell. (coll. P.K. Endress 9035, 07 11
1990, northern Queensland, Australia), floral buds.
Apodytes clusiifolia (Baill.) Villiers (coll. P.K. Endress 6306,
1981, New Caledonia), anthetic flowers.
Apodytes dimidiata E. Mey. ex Arn. (coll. P.K. Endress 2012-1,
04 07 2012, cultivated Botanic Garden of the University of
Zurich), floral buds and anthetic flowers.
Cassinopsis madagascariensis Baill. (coll. P.K. Endress 7810,
10 1987, Madagascar), anthetic flowers.
The material was fixed and storedin 70 % ethanol. Flowers inves-
tigated with scanning electron microscopy (eight anthetic or
slightly preanthetic flowers, of E. harleyi, four slightly prean-
thetic flowers of E. nitens) were critical-point dried, sputter-
coated with platinum and studied at 10 kV with a Zeiss
Supra-50 VP system. The material used for microtome section
series (two anthetic flowers of E. harleyi, two slightly preanthetic
flowers of E. nitens) was dehydrated and embedded in Kulzer’s
Technovit (2-hydroethyl methacrylate). It was infiltrated with
CORNALES
ERICALES
Core lamiids
GARRYALES s.s.
Metteniusaceae
Oncothecaceae
Icacina group
Apodytes group
Emmotum group
Cassinopsis
Other AQUIFOLIALES
Stemonuraceae*
Cardiopteridaceae*
Pennantiaceae*
Other APIALES
DIPSACALES
ASTERALES
Lamiids
Campanulids
Emmotaceae
Icacinaceae s.s.*
GARRYALES s.I.
FIG. 1 . Summary phylogenetic treeof asterids showing the position of represen-
tatives of the former Icacinaceaes.l. (asterisks). Only supported clades are shown.
The polytomy at the base of lamiids reflects lack of support and/or incongruent
results in phylogenetic studies (Karehed, 2001;Lens et al., 2008;Refulio-
Rodriguez and Olmstead, 2014), and the classification mapped on this area of
the tree shows the taxonomic circumscriptions adopted in the text. Icacinaceae
s.s. consist of all representatives of Icacinaceae s.l. that diverge close to the
base of lamiids. The Apodytes,Emmotum and Icacina groups were recognized
by Karehed (2001). The circumscription of the reinstated Emmotaceae was sug-
gested by APG III (2009). Garryales s.l. representsthe expanded order by includ-
ing Garryales s.s. plus representatives of Icacinaceae s.s. as suggested by Karehed
(2001) and APG III (2009).
Endress & Rapini — Floral structure of EmmotumPage 2 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
Technovit solution in ethanol in several steps. Embedded mater-
ial was sectioned using a Microm HM 355 rotary microtome with
a conventional D knife. The 7-mm-thick sections (more than
1000 sections) were stained with ruthenium red and toluidine
blue and mounted in Histomount.
RESULTS
Emmotum harleyi
Inflorescence. Each inflorescence in the axil of a foliage leaf con-
sists of two branches of botryoids. Instead of single lateral
flowers, there are often dyads or triads of flowers in the proximal
region of each branch. Because there are not many flowers ( fewer
than ten per branch), such a branch could be seen as a poor thyr-
soid or a poor panicle (for terminology, see Endress, 2010a). The
two branches are of similar size and are situated one obliquely
behind the other. We were not able to determine whether both
branches are lateral to a very short aborting branch, whether
one of the two branches is lateral to the other, or whether one
of the two branches is an accessory branch. As the two branches
branch right in the axil of the foliage leaf, the topology of this
branching could only be determined in a developmental study.
Flowers. The flowers are pentamerous, probably including the
gynoecium (for interpretation, see below), each organ category
forming one whorl, and all whorls alternating. At anthesis, the
flowers are widely open, the petals are spreading and slightly
reflexed but the stamens are connivent and are more or less con-
tiguous at their tips (Figs 2,3and 4A).
Calyx. The sepals are congenitally united in their lower half and
are triangular in the upper half (Fig. 4D). They are only about half
the length of the petals already in bud and are thus not protective
for the inner floral organs except at the base. The outer surface is
covered with curly unicellular, unlignified hairs. Sepals have
more than one vascular trace. The main trace formed by the
median bundle is accompanied by either two separate lateral
traces or by synlateral traces.
Corolla. The petals are free without any congenitally united basal
region. However, in bud, they are postgenitally connected by
interdigitated epidermal cells at their margins, except for the
very base, where they remain free from each other throughout de-
velopment (Fig. 4B). The dorsal (outer) surface has a dense indu-
mentum of curly unicellular hairs in the upper half, but is
glabrous in the lower half where they were covered by the
sepals in bud (Fig. 4B). The ventral (inner) surface has a
median longitudinal rib with conspicuous long hairs, whereas
the flanks are glabrous (Fig. 4C). The hairs have an irregularly
moniliform shape. In the compact bud, the median rib of each
petal protrudes between the anthers. The petals have a single vas-
cular trace.
Androecium. The stamens are free from each other and also from
the petals. At the floral base, they first fuse with the gynophore for
a short distance. They have a short filament and an elongate, sag-
ittate anther. In the anthetic flower, the filaments are more or less
upright and the anthers are curved inward, their tips meeting in
the centre of the flower over the gynoecium (Fig. 2). During
critical-point drying anthers slightly curve backward so that
they are no longer contiguous in the floral centre (Fig. 4A).
Each of the two thecae has only one pollen sac. The dorsal
pollen sac is not formed. That the remaining pollen sac represents
the ventral one is shown by the position of the longitudinal dehis-
cence line, which is on the dorsal side of the pollen sac (figured
for E. nitens, Figs 7D, E and 8G). The stamens have a single
vascular trace.
Gynoecium. The gynoecium consists of an obovoid main body
and a short, stub-like style with a small stigma (Fig. 4D–F).
FIG.2. Emmotum harleyi. Flowers at anthesis.
FIG.3.Emmotum harleyi. Floral diagram, including floral subtending bract
(xx, two reduced carpels).
Endress & Rapini — Floral structure of Emmotum Page 3 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
The slightly narrower (tapering) basal part is at the level below
the ovary locules and forms a gynophore (Fig. 6A). At anthesis,
the entire gynoecium (including the gynophore) is approx.
1.6 mm long, and the gynophore is approx. 0.4. mm long. The gy-
noecium is glabrous; its surface is not smooth but has papillate
epidermis cells and has imprints by the long hairs of the inner
surface of the petals, which are tightly appressed to the gynoe-
cium in bud (Fig. 4E, F). Likewise, the ovary surface may have
five incomplete longitudinal edges caused by the anthers,
which are appressed to the ovary surface in bud (Fig. 4E). The
tissues of the gynoecium are conspicuous by their high tannin
content at anthesis (Fig. 5). Idioblasts with oxalate druses are
scattered especially in the ovary.
The ovary has three locules, each with two ovules, indicating
the presence of three fertile carpels. For convenience, we call
these ovule-bearing carpels fertile irrespective of whether all
ovules develop into seeds. Most unusually, the three locules
are all on the same side of the ovary (the abaxial side of the
flower), which gives the ovary a conspicuously one-sided, mono-
symmetric shape (Figs 3,4E, F, 5and 6). The three locules are all
at the same level and are of equal size. The outer contour of the
side containing the ovules is slightly bulged, whereas the oppos-
ite side is less curved and less expanded (Fig. 4F). The latter
appears to contain two reduced carpels, as explained below.
Seen from above, there is a Y-shaped slit in the stigma
(Fig. 4E). The forked part of the Y is on the side with the three
locules. Thus, the fork probably marks the delimitations
between the three fertile carpels whereas there are no delimita-
tions between each lateral fertile carpel and its neighbouring
sterile carpel and between the two sterile carpels. The long arm
of the Y is tilted downwards so that in transverse sections it
forms a gap between the two flanks of the gynoecium tip (and
it gives the incorrect impression of a transverse section of a
single carpel) (Fig. 6B).
Analysis of the internal morphology of the gynoecium shows
that it is syncarpous along its whole length. The style is sympli-
cate, and even the uppermost part that seems plicate at first sight
(as explained above) (Fig. 6B, C). The locular part of the ovary is
synascidiate in the lower approx. 85 % of its length (Figs 5D and
6K–M) and symplicate above (including the transition from
ovary to style) (Figs 5A– C and 6D – J). There is a very short
apical septum (as defined by Hartl, 1962) on the bulging side
of the ovary (Figs 5A and 6H). At the level where the style is a
tube, the inner morphological surface is a median slit, which is
more or less gaping on the adaxial side (Fig. 6E). Lower down,
in the roof of the ovary, this slit is also gaping on its abaxial
side (Fig. 6F, G). Downwards, before the two gaps disappear at
the level where the locules appear, the gaps open for a short dis-
tance into one. Its pentagonal shape in transverse section may
reflect the inner surface of five carpels (Figs 5A, B and 6H, I).
At the base of the symplicate zone, the inner morphological
surface forms the three locules and the ventral slits of the three
fertile carpels (Figs 5C and 6J), whereas the two sterile carpels
are no longer apparent. In the synascidiate zone, the inner
ABC
F
E
D
FIG.4. Emmotum harleyi. Scanning electron micrographs. (A) Flower at anthesis. (B) Floral bud, outer suface. Two petals with valvate aestivation and postgenital
connection (arrow).Distribution of hairs reflects position of sepals in younger bud: in areas without hairsthe sepals were appressed to the petals in bud (star). (C) Petal of
anthetic flower, ventral side.Midrib with moniliform hairs. (D) Anthetic flower, showing synsepalous calyx and gynoecium (perianth and androecium removed). (E)
Gynoecium of anthetic flower, from above, fertile side down. Surface with pressure marks of anthers and of moniliform hairs from petals. (F) Gynoecium of anthetic
flower, fromthe side, fertile side at right. Surface with pressure marks of moniliform hairs from petals. Scale bars: (A) ¼1 mm; (B, C, E, F) ¼0.1 mm; (D) ¼0.2 mm.
Endress & Rapini — Floral structure of EmmotumPage 4 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
morphological surface no longer communicates between the
three locules (Figs 5D and 6K, L). The placentae are at the upper-
most level of the synascidiate zone (Fig. 6K).
In the style, the slit formed by the inner morphological surface
is surrounded by several cell layers of small-celled tissue with
relatively thick, dark cell walls, but without distinct vascular
bundles (Fig. 6B, C). At the transition level from the style to
the ovary, outside of the dark-cell-walled area around the inner
morphological surface, three vascular bundles appear in those
radii where lower down the three locules are situated (Fig. 6D).
According to their position, they represent the dorsal bundles
of the three fertile carpels. At the other end of the slit, two
weak bundles appear slightly lower down, which may be the
bundles of two additional, reduced, carpels. Somewhat lower
down, the three bundles of the three fertile carpels depart from
close to the inner surface toward the dorsal side as three anasto-
mosing vascular branches, which form a dense network of
bundles around the ovary (Fig. 6F, G). In the symplicate zone
of the upper ovary, each of the two septa between the three
locules has a synlateral bundle close to its inner angle (Fig. 6I, J).
Distally, these two bundles can be followed up to the transition
toward the style (Fig. 6E– H). Downward, at the level of the pla-
centae, these synlaterals branch and the branches serve the six
ovules (Fig. 6K). Below the placentae, few vascular bundles
remain more or less in the centre of the ovary, before they
connect to the closest part of the peripheral network of bundles
lower down (Fig. 6L). At the base of the gynoecium, in the gyno-
phore, the peripheral network is still present in a simple form
(Fig. 6M) (but compare with Emmotum nitens). The arrangement
of the vasculature does not have a monosymmetric pattern. Thus,
there is no evidence of a difference between the abaxial side and
the adaxial side of the gynoecium, which suggests a regular
carpel arrangement around the circumference of the gynoecium,
and thus the presence of five carpels.
Ovules. The two ovules in each locule are positioned one above
and slightly beside the other (Fig. 6A). Both extend more or
less in the median plane. The upper ovule is more or less horizon-
tally directed, the lower one more vertically. The upper ovule has
the micropyle turned slightly to the right or the left side. In the
A
E
BC
D
FIG.5. Emmotum harleyi. Transverse microtome section series of gynoecium at anthesis (A– D) and longitudinal section of ovule (E). (A) Level of apical septum
(corresponding to Fig. 6H). (B) Level immediately below apical septum (corresponding to Fig. 6I). (C) Lowermost level of symplicate zone (correspondingto Fig.6J).
(D) Uppermost level of synascidiatezone (corresponding to Fig. 6K). (E) Longitudinal section of bitegmic ovule. Signatures: o, outer integument; i, inner integument;
n, nucellus; arrow, undulate contiguous surfaces of ovule and locular wall. Scale bars ¼0.1 mm.
Endress & Rapini — Floral structure of Emmotum Page 5 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
lower ovule, the micropyle is more or less in the median plane.
The ovules are tightly appressed to each other and to the locular
wall and their contiguous surfaces are undulate (Fig. 5E). They
are bitegmic and crassinucellar, but with a thin nucellus
(Fig. 5E). The micropyle is formed by the inner integument. At
the level of the nucellus, the outer integument is three to five
cell layers thick, the inner three or fourcell layers. Above the nu-
cellus, at the rim, both integuments are thicker. A well-
differentiated endothelium is present. Each ovule is served by
one vascular bundle, which ends in the chalaza. It is unknown
whether there is always only a single seed per fruit and
whether this seed develops predominantly in the median or a
lateral locule (Sleumer, 1942).
Nectary. The periphery of the lower part of the ovary and the
upper part of the gynophore is nectariferous (Fig. 6A). The
tissue is full of starch grains. At anthesis, the nectariferous
tissue loses coherence, which causes open spaces as artefacts
in the microtome sections, especially in the upper part of the
nectary.
p
p
sssss
s
s
s*
*
V
C
L
d
d
d
dd
d
dd
d
dd
d
nn
o
o
s
s
A
BC
DE
FG
HI J
KL M
FIG.6. Emmotum harleyi.(A) Schematic reconstruction of median longitudinal sectionof gynoecium at anthesis, with entire (outer and inner) morphological surface.
(B–M) Transverse microtome section series of anthetic gynoecium, line drawings of morphological outer and inner surfaces (thicker lines) and outlines of vascular
bundles (thinner lines). (B) Stigma. (C) Style. (D) Upper level with only the three dorsal bundles of the fertile carpels visible. (E) Upper level with all five dorsal carpel
bundles and the two synlateralbundles visible. (F) Level of mainly dorsal bundle of median fertile carpel slanting and branching over bulged part of ovary. (G) Levelof
mainly dorsal bundles of lateral fertile carpels slantingand branching over bulged part of ovary. (H) Level of apical septumand arrangement of the dorsal carpel bundle
network along the periphery of the ovary.Open space between the five carpels and uppermost level of the locule of the median carpel.(I) Slightlybelow level of apical
septum. (J) Lowermostlevel of symplicate zone. All threelocules present. (K) Uppermost level of synascidiatezone. (L) Mid-level of synascidiate zone. (M) Basal level
of gynophore. Signatures:c, central gaping space delimited by inner morphological surface of gynoecium; d, dorsal carpel vascular bundle; Lm locule; n, nectariferous
tissue; O, ovule; p, placental vascular bundle; s, synlateral carpel vascular bundle; V, ventral slit; asterisk, apical septum; dotted line, delimitation of nectariferous
tissue. Scale bar ¼0.3 mm.
Endress & Rapini — Floral structure of EmmotumPage 6 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
Emmotum nitens
Inflorescence. Inflorescences in E. nitens appear in the axil of
foliage leaves. They are thyrsoids or double thyrsoids. In add-
ition, they have an obliquely transverse accessory branch (bud)
at the base (i.e. without an individual subtending organ).
Because they do not have many flowers (about 12), they can
also be regarded as poor panicles (for terms, see Endress, 2010a).
Flowers. We studied advanced floral buds; anthetic flowers were
not available. Flower morphology is as in E. harleyi. In bud, the
epidermis of all contiguous organs seems to be somehow inter-
dentated. Even the epidermis of the free thecae and the connect-
ive at the base of the sagittate anther are connected in this way.
Calyx. Sepals are short, congenitally united (Fig. 7A). The dorsal
(outer) side of the calyx is densely strigose, with unicellular,
unlignified hairs (Fig. 7B). Each sepal has a median and one or
two smaller lateral bundles. The lateral bundles of adjacent
sepals may or may not form synlateral bundles toward the base.
The median, lateral and synlateral bundles form individual
traces in the floral base. Thus, the number of traces per sepal is
variable. The sepals are highly tanniniferous, especially on the
dorsal (outer peripheral) side.
Corolla. Petals are valvate in bud, free from each other from the
base, but postgenitally connected in bud with zipper-like
interdigitated epidermis except for the floral base where they
remain free (Figs 7B, 8F and 9P). The dorsal (outer) side is
densely hairy with similar but longer hairs than on the sepals
(Fig. 7A, B). Each petal has on its ventral (inner) surface a
median longitudinal rib with long hairs (Fig. 7C). The hairs are
concentrated in two groups (Fig. 7C). In the group of the upper
half of the petal, theyare moniliform but appear to be unicellular,
as seen from microtome sections. In the group of the lower half of
the petal, they are thinner and shorter and appear simpler. Each
petal has a single vascular trace. The dorsal (outer peripheral)
area of the petals is highly tanniniferous (Fig. 8F).
Androecium. Stamens are free from each other. At the floral base,
they first fuse with the gynophore, and not with the perianth
organs. Anthers are slender and sagittate, with monosporangiate
thecae, each with a longitudinal dehiscence line (Figs 7D, E and
8G). In transverse section, they appear extremely introrse at first
sight. However, the dehiscence line is toward the dorsal side of
each theca, which indicates that the dorsal pollen sac has disap-
peared (Fig. 7E). Thus, the introrse appearance of the anther is
mainly caused by the lack of the dorsal pollen sac on each side.
Each stamen has a single collateral vascular bundle and a
single vascular trace. Stamen filaments and connectives show
high tannin contents in their tissues so that they easily tear in
microtome sections (Fig. 8G).
ABC
F
E
D
FIG.7. Emmotum nitens. Scanning electron micrographs. (A) Floral bud shortly before anthesis, from above. (B) Floral bud shortly before anthesis, from the side,
sepals partly removed to show the freebase oftwo petals (arrow). (C) Petal of floral bud shortly before anthesis, ventral side. Midrib with a lower and an upper group of
hairs. (D, E) Stamens of floral bud shortly before anthesis. (D) Ventral side. (E) Dorsal side (P, ventral pollen sac;arrow, dehiscence line). (F) Gynoecium of floral bud
shortly before anthesis, from the side (arrow, stigma; asterisk, nectary). Scale bars: (A, C– F) ¼0.1 mm; (B) ¼0.2 mm.
Endress & Rapini — Floral structure of Emmotum Page 7 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
Gynoecium. The overall shap e of the gyno ecium is as i n E.harleyi.
However, the outer surface is not glabrous but covered with long
unicellular, lignified hairs, except for style, stigma, gynophore
and nectary (Fig. 7F). The apical morphological mouth
(opening) of the gynoecium has the shape of a more or less hori-
zontal slit (Figs 7Fand 9A). In contrast to E. harleyi,itisnot
forked. The gynophore is not attenuated at the base (Fig. 9O, P).
The analysis of the inner morphological surface shows about
the same proportions as in E. harleyi. The style and transition
to the ovary are symplicate (Fig. 9A–I), and the locular part of
the ovary is synascidiate along ca. 75 % of its length in the
lower part (Figs 8D and 9M-O) and symplicate above
(Figs 8B, C and 9J – L). On the bulging side, there is also a
very short apical septum (Figs 8B and 9J).
AB
CD
EFG
FIG.8. Emmotum nitens. Transverse microtome sections of gynoecium shortly before anthesis (A– D) and sections of other floral parts (E– G). (A) Style. Poorly
differentiated vascular bundles indicated (red arrows, dorsal carpel bundles; yellowarrows, synlateral carpel bundles); black arrow, slit-shaped inner morphological
surface of gynoecium. (B) Level of apical septum (corresponding to Fig. 9J). (C) Lowermost levelof symplicate zone (corresponding to Fig. 9L). (D) Uppermost level
of synascidiate zone (corresponding to Fig. 9M). (E) Longitudinal section (more or less median) of bitegmic ovule (o, outer integument; i, inner integument;
n, nucellus). (F) Transverse section of upper part of flower showing two petals that are postgenitally connected with interdigitated epidermal cells (arrows).
(G) Transverse section of anther with monosporangiate thecae (arrows point to prospective dehiscence lines). Scale bars: (A, E, F) ¼0.05 mm; (B –D, G) ¼0.1 mm.
Endress & Rapini — Floral structure of EmmotumPage 8 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
As in E. harleyi, the stigma and upper part of the style are
devoid of vasculature (Fig. 9A, B). Toward the base of the
style, five vascular bundles appear: the three on the abaxial
side of the gynoecium are larger than the two on the adaxial
side (Fig. 9C). They probably correspond to the primary
bundles of the three fertile and the two sterile carpels, respective-
ly. At the transition from the style to the ovary, in addition, a syn-
lateral bundle appears between the median and each of the two
lateral fertile carpels (Figs 8A and 9D). In the ovary, the vascular
pattern (Fig. 9F–O) is as described for E. harleyi. Vascular
bundles serving the ovules connect with the closest area of the
peripheral bundle system basipetally (Fig. 9N, O). At the base
of the gynoecium, in the gynophore, there are five major vascular
strands alternating with the traces of the stamens. Thus, they cor-
respond to the lower portions of the dorsal bundles of the five
carpels.
Ovules. As in E. harleyi, the ovules are bitegmic and crassinucel-
lar (or weakly crassinucellar) (Fig. 8E), and the number and pos-
ition of the ovules in the ovary is also the same. The outer
d
d
dd
d
s
s
ss
s
ss
o
o
p
p
d
d
d
p
d
st
st
d
*
A
BCD
EF G
HI J K
LM N
OP
FIG.9. Emmotum nitens. Transverse microtome section series of gynoeciumshortly before anthesis, line drawings of morphological outerand inner surfaces (thicker
lines) and outlines of vascular bundles (thinner lines). (A) Stigma. (B) Style, above the zone with vascular bundles. (C) Style, zone with only the five dorsal vascular
bundles visible. (D) Style, with the five dorsal and the two synlateral vascular bundles visible. (E) Style, transition to ovary. (F– H) Level of mainly dorsal bundle of
median fertile carpel slanting and branching over bulged part of ovary. (I) Level of mainly dorsal bundles of lateral fertile carpels slanting and branching over bulged
part of ovary.(J) Level of apical septum and arrangement of the dorsal carpel bundle network along the periphery of the ovary. (K) Slightlybelow level of apical septum.
(L) Lowermost level of symplicate zone. (M) Uppermost level of synascidiate zone. (N) Mid-level of synascidiate zone. (O) Lowermost level of synascidiate zone,
locule of the lateral fertile carpel on the left stillpresent (arrow). (P) Level at the base of the gynophorewith the five main (dorsal) carpel vascular bundles. In addition,
petals and stamens and their vascular bundles are shown to visualize the alternation of the three inner organ whorls. Signatures: d, dorsal carpel vascular bundle;
o, ovular vascular bundle; p, petal vascular bundle; s, synlateral carpel vascular bundle; st, stamen vascular bundle; asterisk, apical septum; dotted line, delimitation
of nectariferous tissue. Scale bar ¼0.3 mm.
Endress & Rapini — Floral structure of Emmotum Page 9 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
integument is three or four cell layers thick, the inner is three cell
layers thick. The micropyle is formed by the inner integument
(Fig. 8E). A distinct endothelium is present (Fig. 8E).
Nectary. As in E. harleyi, there is a nectary at the periphery of the
gynophore. In floral bud, it is small-celled and cytoplasm-rich.
Starch is not found at this stage.
DISCUSSION
Flower
Flowers with similarly expanded and somewhat recurved petals
and connivent stamens as in Emmotum are also known from
Ottoschulzia (Icacinaceae s.s.)(Santiago-Valentı
´n and Viruet-
Oquendo, 2013). Furthermore, the anthers may have a similar
morphology in both genera (see below, under Androecium).
Calyx
As in Emmotum, in most Icacinaceae s.l., the calyx remains
short, much shorter than the petals. The sepals are congenitally
united in the lower portion and have a short free distal part.
Thus, the sepals function as a protective device for the inner
floral organs only in early stages of floral development.
Corolla
In Icacinaceae s.l., petals are commonly valvate and protective
organs in flower buds, as in Emmotum (but they are quincuncial-
imbricate in Cardiopteridaceae: Tobe, 2012; and Oncothecaceae:
Dickison, 1986). Also, the presence of a longitudinal rib on the
upper (ventral) side of the petals is common, and in a few
genera, there are tufts of long hairs on this rib (Emmotum and
Icacina)(Sleumer, 1942). That such hairs are moniliform, as
observed here, was not noticed before in Emmotum (Howard,
1942a;Sleumer, 1942). The moniliform shape of these hairs
appears not to be formed by multicellularity, in contrast to mo-
niliform hairs in flowers of many other plants (Endress, 1994),
but just by differential expansion of the wall of a single long
cell. It should be studied in the field whether these hairs have a
function in secondary pollen presentation, as theyare located ad-
jacent to the pollen sacs in bud. Petals with a longitudinal rib on
the upper side are also known from some Stemonuraceae
(Utteridge, 2011). The petals are mostly free from each other
in Icacinaceae s.l. However, they are united in Calatola,
Ottoschulzia and Platea of Icacinaceae s.s., and Acrocoelium,
Dendrobangia,Gonocaryum and Leptaulus of Cardiopteridaceae
(Sleumer, 1942), and in Metteniusaceae (Sleumer, 1942;
Gonza
´lez and Rudall, 2010) and Oncothecaceae (Dickison,
1986). Petals are lacking in Garryales, except for Aucuba,
whose petals are shortly congenitally united (Reidt and Leins,
1994). Whether the basal petal union in these groups is congeni-
tal or only postgenital is, however, unknown in most of the other
cases.
Androecium
As in Emmotum, the stamens are mostlyfree fromthe petals in
Icacinaceae s.l. However, in some cases in which the petals are
basally fused into a tube, the stamens are also fused with this
tube, such as in Dendrobangia (Rusby, 1897),Gonocaryum
(Sleumer, 1971) and Leptaulus (Rusby, 1897) (all three in
Cardiopteridaceae), and in Metteniusaceae (Sleumer, 1942;
Gonza
´lez and Rudall, 2010).
That the thecae are monosporangiate in Emmotum has been
stated earlier but seems to have been forgotten and is not men-
tioned in more recent literature (such as Takhtajan, 1997,2009;
Stevens, 2001 onward; de Stefano and Ferna
´ndez-Concha,
2011). Miers (1851 –1861, p. 53, plates 21 and 22) found that
Emmotum (representing his tribe Emmoteae) differs from all
other Icacinaceae s.l. ‘in its plurilocular ovarium, and the singular
structure of its anthers, which are bilobed, and consist of two uni-
locular, evalvate and boat-shaped pollen cells’, and van Tieghem
(1897, p. 120) clearly stated: ‘L’e
´tamine n’a dans son anthe
`re,
de chaque co
ˆte
´de la co
ˆte me
´diane, qu’un seul sac pollinique,
s’ouvrant par une fente longitudinale situe
´e dans l’angle
externe’ (‘the stamen has on both sides of the median plane of
the anther only one pollen sac, opening by a longitudinal slit on
the outer side’). Howard (1942a, p. 482) mentioned that ‘[t]he
thecae of the anthers are reduced to two’, thus confusing thecae
with pollen sacs. The early description by Engler (1872,p.43),
‘loculis ...margineposteriore a connectivo omnino soluto extror-
sum dehiscentibus’(‘with the locules on the posterior margincom-
pletely detached from the connective and extrorsely dehiscing’), is
not explicit but seems to point to this fact, and this vague phrasing
is repeated in Engler (1896) and Sleumer (1942). However, Engler
(1896, p. 240), in his general description of the family, mentioned
that all Icacinaceae, except Polyporandra, have four-locular
anthers. Thus, he appears to have overlooked the monosporangiate
structure of the thecae in Emmotum.
The presence of monosporangiate thecae has not been described
from any other Icacinaceae s.l. Howard (1942b, p. 32) mentioned
for Ottoschulzia that ‘dehiscence of the anther is along the junction
with the connective’, which may suggest similar monosporangiate
thecae as in Emmotum. Although Howard(1942a, p. 482) also men-
tioned that the anthers of Poraqueiba and Oecopetalum have a
similar dehiscence as Emmotum,forPoraqueiba, he explicitly
mentioned dorsal and ventral pollen sacs (Howard, 1942b, p. 50)
and for Oecopetalum, when distinguishing it from Poraqueiba,
he did not mention a difference in the anthers (Howard, 1942b,
p. 35). The only other recognized deviation from the ground
pattern of angiosperm stamens among Icacinaceae s.l. is in
Polyporandra, which has anthers with numerous microsporangia
that open separately and thus lack thecal organization (Sleumer,
1942;Endress and Stumpf, 1990). In Metteniusa, the long,
slender anthers have four pollen sacs but each pollen sac is transver-
sally subdivided into several microsporangia (Gonza
´lez and Rudall,
2010). Another speciality in Metteniusa is that the two pollen sacs of
a theca are relatively far apart from each other and each pollen sac
has a separate dehiscence line (Gonza
´lez and Rudall, 2010).
Gynoecium
Pseudomonomerous gynoecia, i.e. gynoecia that seem to
consist of one carpel but actually have more than one carpel,
are known from a number of angiosperms. In many cases,
these are bicarpellate gynoecia with one carpel sterile, as
shown by Eckardt (1937), in his classical study, which concen-
trated mainly on families of the former Urticales (now in
Rosales, APG III, 2009). But Eckardt (1937) also showed
Endress & Rapini — Floral structure of EmmotumPage 10 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
pseudomonomery in a number of gynoecia with more than two
carpels. However, to our knowledge, one-sided pseudotrimerous
gynoecia (with three fertile carpels on one side and additional,
sterile, carpels on the other) as in Emmotum are not known
from any other angiosperm. Also, pseudodimerous gynoecia
are exceptional in angiosperms. Pelliciera (Tetrameristaceae,
Ericales) has two locules (Kobuski, 1951;Stevens, 2001
onward; Kubitzki, 2004), but the flowers may be pentamerous
as reported by Scho
¨nenberger et al. (2010) and confirmed in
more detail to be pentamerous by von Balthazar and
Scho
¨nenberger (2013). However, in contrast to Emmotum, the
locules are, in addition, not one-sided in Pelliciera.
Gonza
´lez and Rudall (2010, p. 203) stated that their ‘results
[on Metteniusa] open up the possibility that, apart from Mette-
niusaceae and Oncothecaceae, other putatively basal lamiids
that possess two pendant ovules (e.g. Garryales, Cardiopterida-
ceae, and Icacinaceae s.s.) could also show cryptic pseudomo-
nomery’. In fact, it has long been assumed that representatives
of these groups have pseudomonomerous gynoecia (Engler,
1872,p.41;Baillon, 1874,p.202;Sleumer, 1942, pp. 323, 337;
Fagerlind, 1945, p. 350) and more conspicuously so if there are
two stigmatic branches (Eucommia;Eckardt, 1957). These
earlier authors noted that the seemingly unicarpellate gynoecia in
these groups had additional, sterile carpels, although the term
‘pseudomonomerous’ was only introduced by Eckardt (1937).
Garrya commonly has two styles and two ovules in the single
locule or, more rarely, three styles accompanied by three ovules
(Hallock, 1930;Eyde, 1964). This suggests that the gynoecium is
not pseudomonomerous in Garrya but that each carpel has one
ovule. However, there is no critical study focusing on this question
in Garrya,andAucuba has not been studied in this respect either.
The gynoecium of Cardiopteris (Cardiopteridaceae, Aquifoliales)
was interpreted as bicarpellate-pseudomonomerous (Tobe, 2012)
or tricarpellate (Kong et al., 2014).
For Emmotum,van Tieghem (1897, p. 120) and Howard
(1942a, p. 482) assumed a pentamerous gynoecium, of which
three carpels are fertile and the other two are strongly reduced
and without locules. However, according to Stevens (2001
onward), the gynoecium is trimerous and has two sterile but
only one fertile carpel with two septa. The latter interpretation
is likely to be incorrect because each of the three fertile portions
has two obliquely collateral ovules, which would not be expected
in a single septate carpel. Each of the three locules in Emmotum
has the same structure concerning ovule position as the single
fertile locule in other Icacinaceae s.l. However, it is unclear
whether the gynoecium of Emmotum evolved from a pentamer-
ous gynoecium with all carpels fertile (such as in Oncotheca)by
reduction of fertility or from a trimerous gynoecium with one
fertile carpel (such as in probably most Icacinaceae s.s.)byan
increase in fertile carpel number.
The question remains whether there are one or two sterile
carpels in the gynoecium of Emmotum and other Icacinaceae,
and thus whether a trilocular gynoecium of Emmotum consists
of four or five carpels. The outer ovary surface is slightly
five-angular. However, this shape is superimposed by the five
anthers, which imprint the slightly angular shape in bud (see
Endress, 2008, for imprinted shape in general) and has probably
nothing to do with gynoecium pentamery. The vasculature of the
ovary is complex. However, in the upper part of the adaxial side
of the gynoecium, there are two relatively distinct vascular
bundles (in both Emmotum species here studied), which are
best interpreted as the two main (dorsal) bundles of the two
reduced carpels. These two bundles have three counterparts in
the radii of the three fertile locules. At the base of the gynoecium,
in the gynophore, there are five main vascular bundles, alternat-
ing with the stamen vascular bundles in Emmotum nitens (shortly
before anthesis). They are in the same radii as the five primary
(dorsal) carpel bundles in the style. Thus, they can only be inter-
preted as the lowermost portions of five carpel dorsal bundles.
Thus, this is a strong argument that the gynoecium has two
sterile carpels, in addition to the three fertile carpels. In
E. harleyi there are several groups of bundles, which still form
a network at this level (at anthesis). The gynoecium does not
show separate tips of the carpels. However, in E. harleyi, two
radial furrows on the abaxial side of the stigma may mark the
borders between the three fertile carpels. The rim of the stigma
is more or less horizontal in E. nitens, but somewhat oblique in
E. harleyi. From drawings in the literature, the degree of oblique-
ness of the rim varies in Icacinaceae s.s., depending on stigma
(and style) length, e.g. strongly oblique in Apodytes (Potgieter
and van Wyk, 1994b, fig. 8) and Mappia (Sleumer, 1942, fig.
97E). Even within the genus Emmotum, there are also species
with a longer style (Sleumer, 1940).
Emmotum is exceptional in Icacinaceae s.l. in having three
locules formed by three fertile carpels. All other genera have a
single locule formed by a single fertile carpel. The latter is
even true for the genus Pyrenacantha, with numerous stigmatic
lobes, which simulate a multicarpellate gynoecium (Endress,
2014).
In summary, the completely syncarpous gynoecium of
Emmotum is most likely pseudotrimerous with three fertile and
two sterile carpels, which is indicated by the following features:
(1) the three fertile carpels radiate at such an angle that the pres-
ence of two additional, reduced carpels on the opposite side of
the gynoecium leads to an approximately polysymmetric ar-
rangement of the five carpels; (2) the inner morphological
surface of the gynoecium on top of the ovary forms a five-angular
opening, which fits with a pentamerous gynoecium; (3) there are
five main vascular bundles in the style, which correspond to the
primary vascular bundles of the five carpels; (4) there are five
main vascular bundles in the gynoecium base (in E. nitens),
above the level of the joining vasculature of the outer floral
organs, alternating with the five stamens – the five main vascular
bundles at this level are the lowermost parts of the primary vas-
cular bundles of the five carpels.
Ovules
Ovules are poorly known in Icacinaceae s.l., especially in Ica-
cinaceae s.s. Emmotum seems to be the only known Icacinaceae
s.l. with two well-developed integuments (this study). According
to Fagerlind (1945),Phytocrene (Icacinaceae s.s.) has a transient
bitegmic phase during development, and in this phase bitegmy is
only weakly expressed. Other Emmotaceae cursorily studied
here, Apodytes clusiifolia and Cassinopsis madagascariensis,
appear to be unitegmic. In the literature, unitegmic ovules are
specifically mentioned from the following genera of Icacinaceae
s.s.:Apodytes,Desmostachys,Leretia,Poraqueiba,Rhaphiosty-
lis (Mauritzon, 1936a), Iodes and Pyrenacantha (Mauritzon, in
Sleumer, 1942) and Metteniusa (Metteniusaceae; Gonza
´lez
Endress & Rapini — Floral structure of Emmotum Page 11 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
and Rudall, 2010); of Stemonuraceae: Gomphandra (Fagerlind,
1945;Padmanabhan, 1961) and Stemonurus (Mauritzon,
1936a); of Cardiopteridaceae: Citronella (as Villaresia), Lep-
taulus (Mauritzon, 1936a) and Gonocaryum (Fagerlind 1945);
and of Oncothecaceae: Oncotheca (Carpenter and Dickison,
1976;Dickison, 1986). Icacinaceae s.l. were generally character-
ized as unitegmic by Mauritzon (1936b).Cardiopteris (Cardiop-
teridaceae) has orthotropous, ategmic ovules (Kong et al., 2014).
The ovules of the studied species of Icacinaceae s.l. were
described as crassinucellar (Padmanabhan, 1961), weakly cras-
sinucellar (Mauritzon, 1936a), incompletely tenuinucellar or
crassinucellar (Fagerlind, 1945), almost or completely tenuinu-
cellar (Mauritzon, 1936b), tenuinucellar (Mauritzon in
Sleumer, 1942), and probably tenuinucellar (Gonza
´lez and
Rudall, 2010). In Emmotum, they are crassinucellar, but with a
relatively thin nucellus (this study). In Oncothecaceae, they are
crassinucellar (Carpenter and Dickison, 1976;Dickison,
1986). Among Garryales in the circumscription of APG III
(2009), all three genera have crassinucellar, unitegmic ovules
and, as described by Endress (2010b), they are anticampylotro-
pous, i.e. curved in the opposite direction of a campylotropous
ovule (Garrya:Kapil and Rao, 1966;Eucommia:Tang, 1962;
Eckardt, 1963;Sogo and Tobe, 2006;Aucuba:Palm and
Rutgers, 1917;Sato
ˆ, 1971,1976;Alimova and Shinkina, 1987).
At a higher level, bitegmic ovules occur in some basal asterids
(some Ericales), but are extremely rare in euasterids (see
Endress, 2011;Friis et al., 2013). According to our extensive lit-
erature search, in lamiids they are known only from Vahlia
(Vahliaceae) (Raghavan and Srinivasan, 1942) and perhaps
weakly and transiently also in Phytocrene (Icacinaceae s.s.)
(Fagerlind, 1945). Therefore, to discover pronounced bitegmic
ovules also in Emmotum (Icacinaceae s.s. or Emmotaceae) in
this study was a surprise. Vahlia is also otherwise unusual in
lamiids and asterids because of the completely tenuinucellar
ovules and the lack of a vascular bundle in the ovules (Raghavan
and Srinivasan, 1942;Krach, 1976), both features more common
in Lamiales and Gentianaceae (Endress, 2011), although the
genus seems to be closer to Solanales (Refulio-Rodriguez and
Olmstead, 2014). In campanulids, bitegmic ovules are only
known from Quintinia (Paracryphiales) (Friis et al., 2013).
Floral structure of Icacinaceae s.l. and Oncothecaceae
We include the entire Icacinaceae s.l. to show what is similar
and what is different in the segregated groups of this polyphyletic
family. Emmotum (this study) and Metteniusa (Gonza
´lez and
Rudall, 2010) are similar in some respect. Floral organs are
very crowded in bud so that there is a lot of imprinted shape in
bud (see Endress, 2008) at the supracellular and the cellular
level (wavy surfaces of contiguous organs, such as ovules and
locule surface, imprint of edges of anthers and of petal hairs on
the gynoecium surface and mutually indented epidermal cells
of contiguous organs). Petals are valvate. The gynoecium
appears to be basically pentamerous, but is different in detail
(see below). Similarly indented epidermal cells in floral buds
were also found in Ericales (basal asterids; von Balthazar and
Scho
¨nenberger (2013).
Cardiopteris (Tobe, 2012) has quite different flowers. Floral
organs are not crowded and not hairy. Petals are quincuncial-
imbricate, not valvate. The gynoecium, although pseudomono-
merous as commonly in Icacinaceae s.l., is different in detail
(Tobe, 2012;Kong et al., 2014).
The potential relationship between Oncotheca and Emmotum
(both in a possible clade also including the Apodytes group and
Cassinopsis), as suggested by Lens et al. (2008), is supported
by the shared presence of monosporangiate thecae in Emmotum
and Oncotheca. In both cases, the dorsal pollen sacs are lacking
(for Oncotheca, see Dickison, 1986;Endress and Stumpf,
1990). This lack of the dorsal pollen sacs may represent a synapo-
morphy or an apomorphic tendency for this clade.
The gynoecium in Icacinaceae s.l. is probably pseudomono-
merous in general (pseudotrimerous in Emmotum). Although
gynoecium structure is not known in detail for most genera,
there are probably one or two (or more) sterile carpels involved
in many cases (e.g. Sleumer, 1942;Gonza
´lez and Rudall,
2010). The position of the fertile part of the gynoecium is
abaxial in Emmotum in those lateral inflorescence branches
without bracts (this study). Engler (1872) figured a floral
diagram of Emmotum with the fertile part directed downward,
which probably means directed to the abaxial side, but he did
not indicate the position of the subtending bract of the flower.
Also, it has not been studied whether the abaxial position of
the fertile part is a common feature in Icacinaceae s.l. Neither
Engler (1872,1896) nor Sleumer (1942) provided any other
floral diagrams of Icacinaceae s.l. However, Engler’s floral
diagram of Emmotum is incorrect in another aspect because it
shows the carpels opposite the stamens, whereas in reality they
alternate with the stamens, as expected (Figs 3and 9P).
In Cardiopteris, the fertile carpel is adaxial according to Tobe
(2012).Gonza
´lez and Rudall (2010) constructed a diagram for
the gynoecium of Metteniusa but did not determine its orienta-
tion in relation to the subtending bract of the flower. They inter-
preted the placentation in Metteniusa as parietal; thus, the
placenta would be in the symplicate zone and the two ovules
would belong to two carpels. If their interpretation is correct,
Metteniusa would be very different from Emmotum, where the
axile placentae are in the synascidiate zone and the three pairs
of ovules are each in one carpel. They did not take into consider-
ation the potential presence of solid reduced carpels as Eckardt
(1937) showed for many pseudomonomerous gynoecia or the
ontogenetic ‘shift’ of sterile carpels by differential growth of
the gynoecium and resulting restriction of the sterile carpels to
the upper part of the gynoecium as in some Anacardiaceae
(Bachelier and Endress, 2007,2009).
In a number of Icacinaceae s.l., the ovary is conspicuously one-
sided, the sterile sector developing into a coloured, fleshy part in
fruit. This is known, for example, from Apodytes (Potgieter and
van Wyk, 1994b), which is presumably closely related to
Emmotum (Lens et al., 2008;APG III, 2009). However, it
also occurs in some genera that do not belong to Icacinaceae
s.s.; one of the most conspicuous cases is Irvingbaileya
(Stemonuraceae) (P.K. Endress, pers. observ.). Other genera
with such one-sided fruits are listed in Potgieter and van Wyk
(1994b). Interestingly, although the ovary in Emmotum is con-
spicuously one-sided at anthesis, it does not develop such a con-
trasting part in fruit and its fruits are described as drupes (Engler,
1896;Mazine-Capelo and Souza, 2006). The fruits of our collec-
tions of Emmotum are not mature.
Endress & Rapini — Floral structure of EmmotumPage 12 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
Floral structure of basal lamiids in general
Flowers are mostlysmall, less than 1 cm long. Sepals are con-
genitally united at the base, short, not protecting the inner flower
organs in advanced bud. Petals are mostly free, but lacking in
Garryales (except for Aucuba). They are mostly valvate, post-
genitally connected in bud but opening at anthesis (but not con-
nected for a short distance at the very base). They are basally
fused into a short tube in only few Icacinaceae s.l. (Sleumer,
1942) and in Aucuba (Reidt and Leins, 1994). In Metteniusa,
they are fused together with the stamens into a short tube
(Sleumer, 1942;Gonza
´lez & Rudall, 2010). The same is true
for Oncotheca, but here they are quincuncial-imbricate above
the tube (Dickison, 1986).
Stamens are in a single whorl, free from each other, but fused
with the corolla tube in Metteniusa and Oncotheca,asjust
mentioned. The anthers have monosporangiate thecae in
Oncotheca (Dickison, 1986),Emmotum (this study) and, per-
haps, in other unstudied Emmotaceae (see above). Gynoecia
include one or two sterile carpels (not in Oncotheca), and
mostly two or three carpels in total, rarely reaching five
carpels (Emmotum,Metteniusa and Oncotheca). There are
mostly two more or less collateral, anatropous, pendant
ovules per fertile carpel, but only one in Aucuba and Garrya.
Ovules are crassinucellar, but with relatively thin nucellus.
They are unitegmic (except in Emmotum and perhaps weakly
and transiently in Phytocrene).
Floral structure of basal asterids, basal lamiids and basal
campanulids
Sepals are congenitally united, short, not protecting the inner
floral organs in advanced bud in Cornaceae, Icacinaceae s.l. and
Aquifoliaceae, but diverse in Ericales and other Cornales than
Cornaceae. Petals are free or united. They are mostly valvate,
postgenitally connected in bud in Cornaceae, Phyllonomaceae
(Tobe, 2013) and Icacinaceae s.l., but not in Cardiopteridaceae
or Oncothecaceae, where they are quincuncial-imbricate. Also
in Ericales and Cornales other than Cornaceae, sepals and
petals are often imbricate.
Stamens are in a single whorl in some Cornales, some
Ericaceae and all Icacinaceae s.l. But two stamen whorls occur
in some Ericales and some Cornales, and polyandry in some
Hydrangeaceae and Loasaceae of Cornales and in some
Ericales (especially Actinidiaceae, Ebenaceae, Lecythidaceae,
Marcgraviaceae, Sapotaceae, Sarraceniaceae, Symplocaceae
and Theaceae). Anthers with monosporangiate thecae occur in
Grubbiaceae (Cornales), Oncothecaceae (Dickison, 1986;
Endress & Stumpf, 1990), Emmotum (this study) and possibly
in other Emmotaceae (or Icacinaceae s.s.).
Gynoecia with one or two of the carpels sterile generally occur
in Icacinaceae s.l., and thus in both basal lamiids and basal cam-
panulids, but are not common in either basal asterids or other
lamiids and campanulids. Two collateral ovules (more rarely
one) per locule are present generally in Icacinaceae s.l. but not
in Cornales (in some only one ovule, in others more than two),
Ericales (often one or more than two ovules), or other
Aquifoliales (one ovule). Ovules are often crassinucellar (in con-
trast to more derivedlamiid s and campanulids) and havean endo-
thelium (Endress, 2011).
CONCLUSIONS
The three outstanding floral features of Emmotum mentioned in
the title of this paper are of particular interest at different evolu-
tionary levels. (1) A pseudotrimerous gynoecium with three
fertile carpels on one side and two reduced carpels on the other
side is unique at the level of the angiosperms to our knowledge.
This pattern was already described earlier for Emmotum, but in
this paper it was critically analysed for the first time. (2)
Conspicuously bitegmic ovules are exceptional at the level of
the lamiids because they are so far only known from Emmotum,
where they were found for the first time in this study, and from
Vahlia (probably Solanales). All other lamiids have unitegmic
ovules to our knowledge. Finally, (3) monosporangiate thecae
were described 150 years ago in Emmotum but then forgotten
in the later literature and refound again in the present study.
They are of particular interest because they are not very common
in angiosperms but also occur in Oncothecaceae. The function of
this feature is unknown in these clades. Interestingly, similar
monosporangiate thecae with disappearance of the dorsal
pollen sacs are ubiquitous in Asclepiadoideae of Apocynaceae,
a large clade of more advanced lamiids, where the reduced
pollen sac took over an important function in pollination in
forming guide rails for the application of pollinaria. However,
the evolution of their monosporangiate thecae took an inde-
pendent course from disporangiate thecae. At a lower systematic
level, it would be of interest to know whether there are other
Emmotaceae or Icacinaceae s.s. with monosporangiate thecae.
We did not find any explicit mention in the literature. However,
from how stamens are described in some genera, it is possible
that there are many such cases. Ottoschulzia,Poraqueiba and
Oecopetalum would be potential candidates for study.
It is puzzling that basal branches of the two large subclades of
euasterids, lamiids and campanulids, have flowers with a corre-
sponding suite of features, whereas this suite is largely lacking
in the basal asterids on the one hand and in the more advanced
lamiids and campanulids on the other. Is it a synapomorphy of
euasterids? This will need broad comparative studies on all
these groups for evolutionary reconstructions. However, ele-
ments of this suite of features are also common in some more
advanced euasterids, such as only short sepals and valvate
petals that are protective in floral buds.
ACKNOWLEDGEMENTS
For advice in sectioning flowers of Emmotum, we thank Merran
Matthews. For preparing microtome sections of the genera other
than Emmotum, we thank Ruth Jacob and Rosemarie Siegrist.For
support with scanning electron microscopy, we thank Klaus
Marquardt, Center for Microscopy and Image Analysis,
University of Zurich. A.R. is supported by a PQ-1D research
grant from Conselho Nacional de Desenvolvimento Cientı
´fico
e Tecnolo
´gico (CNPq).
LITERATURE CITED
Alimova GK, Shinkina NA. 1987. Aucubaceae. In: Yakovlev MS, ed.
Comparative embryology of flowering plants: Davidiaceae-Asteraceae.
Leningrad: Nauka, 21– 24.
APG III (The Angiosperm Phylogeny Group). 2009. An update of the
Angiosperm Phylogeny Group classification for the orders and families of
Endress & Rapini — Floral structure of Emmotum Page 13 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
flowering plants: APG III. Botanical Journal of the Linnean Society 161:
105–121.
Bachelier JB, Endress PK. 2007. Development of inflorescences, cupules and
flowers in Amphipterygium, and comparison with Pistacia (Anacardiaceae).
International Journal of Plant Sciences 168: 1237–1253.
Bachelier JB, Endress PK. 2009. Comparative floral morphology and anatomy
of Anacardiaceae and Burseraceae (Sapindales), with a special focus on gy-
noecium structure and evolution. Botanical Journal of the Linnean Society
159: 499– 571.
Baillon H. 1874. Deuxie
`me e
´tude sur les Mappie
´es (suite). Adansonia 11:
187–203.
Carpenter CS, Dickison WC. 1976. The morphology and relationships of
Oncotheca balansae.Botanical Gazette 137: 141– 153.
de Stefano RD, Ferna
´ndez-Concha GC. 2011. Morphology-inferred phyl-
ogeny and revision of the genus Emmotum (Icacinaceae). Annals of the
Missouri Botanical Garden 98: 1–27.
de Stefano RD, Angulo DF, Stauffer FW. 2007. Emmotum harleyi, a new
species from Bahia, Brazil, and lectotypification of other Icacinaceae.
Novon 17: 306– 309.
de Stefano RD, Janovec JP, Can LL. 2013. Threedecades to connect the sexes:
Calatola microcarpa (Icacinaceae), a new species from the Southwestern
Amazon. Phytotaxa 124: 43– 49.
Dickison WC. 1986. Further observations on the floral anatomy and pollen
morphology of Oncotheca (Oncothecaceae). Brittonia 38: 249– 259.
Eckardt T. 1937. Untersuchungen u
¨ber Morphologie, Entwicklungsgeschichte
und systematische Bedeutung des pseudomonomeren Gynoeceums. Nova
Acta Leopoldina, n.F. 5: 1– 112.
Eckardt T. 1957. Zur systematischen Stellung von Eucommia ulmoides.
Berichte der Deutschen Botanischen Gesellschaft 69: 487– 498.
Eckardt T. 1963. Some observations on the morphology and embryology of
Eucommia ulmoides Oliv. Journal of the Indian Botanical Society 42A:
27– 34.
Endress PK. 1994. Diversity and evolutionary biology of tropical flowers.
Cambridge: Cambridge University Press.
Endress PK. 2008. The whole and the parts: relationships between floral archi-
tecture and floral organ shape, and their repercussions on the interpretation
of fragmentary fossils. Annals of the Missouri Botanical Garden 95:
101–120.
Endress PK. 2010a.Disentanglingconfusions in inflorescence morphology: pat-
terns and diversity of reproductive shoot ramification in angiosperms.
Journal of Systematics and Evolution 48: 225–239.
Endress PK. 2010b.Flowerstructure and trends of evolution in eudicots and their
major subclades. Annals of the Missouri Botanical Garden 97: 541–583.
Endress PK. 2011. Angiosperm ovules: diversity, development, evolution.
Annals of Botany 107: 1465–1489.
Endress PK. 2014. Multicarpellate gynoecia in angiosperms: occurrence,devel-
opment, organization and architecturalconstraints. Botanical Journal of the
Linnean Society 174: 1– 43.
Endress PK, Stumpf S. 1990. Non-tetrasporangiatestamens in the angiosperms:
structure, systematic distribution and evolutionary aspects. Botanische
Jahrbu
¨cher fu
¨r Systematik 112: 193– 240.
Engler A. 1872. Icacineae. In: Martius CFP, Eichler AW, eds. FloraBrasiliensis,
Vol. 12, pars 2. Leipzig: Fleischer, 40–62.
Engler A. 1896. Icacinaceae. In: Engler A, Prantl K, eds. Die natu
¨rlichen
Pflanzenfamilien, Part III, Section 5. Leipzig: Engelmann, 233–257.
Eyde RH. 1964. Inferior ovary and generic affinities of Garrya.American
Journal of Botany 51: 1083–1092.
Fagerlind F. 1945. Bau des Gyno
¨ceums, der Samenanlage und des
Embryosackes bei einigen Repra
¨sentanten der Familie Icacinaceae.
Svensk Botanisk Tidskrift 39: 346– 364.
Friis EM, Pedersen KR, Endress PK. 2013. Floral structureof extant Quintinia
(Paracryphiales, campanulids) compared with the Late Cretaceous
Silvianthemum and Bertilanthus.International Journal of Plant Sciences
174: 647– 664.
Gonza
´lez FA, Rudall PJ. 2010. Flowerand fruit characters in the early-divergent
lamiid family Metteniusaceae, with particular reference to the evolution of
pseudomonomery. American Journal of Botany 97: 191– 206.
Gonza
´lez FA, Betancur J, Maurin O, Freudenstein JV, Chase MW. 2007.
Metteniusaceae, an early-diverging family in the lamiid clade. Taxon 56:
795–800.
Hallock FA. 1930. The relationships of Garrya. The development of the flowers
and seeds of Garrya and its bearing on the phylogenetic position of the
genus. Annals of Botany 44: 771–812.
Hartl D. 1962. Die morphologische Natur und die Verbreitung des
Apikalseptums. Beitra
¨ge zur Biologie der Pflanzen 37: 241 –330.
Howard RA. 1942a.Studies of the Icacinaceae. III. A revision of Emmotum.
Journal of the Arnold Arboretum 23: 479–494.
Howard RA. 1942b.Studies of the Icacinaceae. IV. Considerations of the New
World genera. Contributions from the Gray Herbarium of Harvard
University 142: 3– 60.
Kapil RN, Rao PRM. 1966. Studies of the Garryaceae. II. Embryology and sys-
tematic position of Garrya Douglas ex Lindley. Phytomorphology 16:
564–578.
Karehed J. 2001. Multiple origins of the tropical forest tree family Icacinaceae.
American Journal of Botany 88: 2259 –2274.
Kobuski CE. 1951. Studies in the Theaceae XXII. The genus Pelliciera.Journal
of the Arnold Arboretum 32: 256– 262.
Kong D-R, Schori M, Lu S-G, Li L, Peng H. 2014. Floral development of
Cardiopteris, with emphasis on gynoecial structure and ovular morphology.
Journal of Systematics and Evolution, in press. doi:10.1111/jse.12081.
Krach JE. 1976. Samenanatomieder Rosifloren I. Die Samen der Saxifragaceae.
Botanische Jahrbu
¨cher fu
¨r Systematik 97: 1– 60.
Kubitzki K. 2004. Pellicieraceae. In: Kubitzki K, ed. The families and genera of
vascular plants, Vol. 9. Berlin: Springer, 297– 299.
Lens F, Karehed J, Baas P, et al. 2008. The wood anatomy of the polyphyletic
Icacinaceae s.l. and their relationships within asterids. Taxon 57: 525–552.
Mauritzon J. 1936a.Embryologische Angaben u
¨ber Stackhousiaceae,
Hippocrateaceae, und Icacinaceae. Svensk Botanisk Tidskrift 30: 541– 550.
Mauritzon J. 1936b.Zur Embryologie und systematischen Abgrenzung der
Reihen Terebinthales und Celastrales. Botaniska Notiser 1936: 161– 212.
Mazine-Capelo FF, Souza VC. 2006. Icacinaceae. In: Cavalcanti TB, ed. Flora
do Distrito Federal, Brasil, Vol. 5. Brası
´lia: Embrapa Recursos Gene
´ticos e
Biotecnologia, 85– 89.
Miers J. 1851–1861. Contributions to botany, Vol. 1. London: Williams and
Norgate.
Padmanabhan D. 1961. A contribution to the embryology of Gomphandra poly-
morpha.Proceedings of the National Institute of Science of India B 27:
389–398.
Palm B, Rutgers AAL. 1917. The embryology of Aucuba japonica.Recueil des
Travaux Botaniques Ne
´erlandais 14: 119– 126.
Potgieter MJ, van Wyk AE. 1994a.Fruit structure of the genus Cassinopsis
Sond. (Icacinaceae) in Africa. South African Journal of Botany 60:
117–122.
Potgieter MJ, van Wyk AE. 1994b.Fruit structure of the southern African
species of Apodytes E. Meyer ex Arn. (Icacinaceae). Botanical Journal of
the Linnean Society 115: 221–233.
Raghavan TS, Srinivasan VK. 1942. A contribution to the life-history of Vahlia
viscosa Roxb. and Vahlia oldenlandioides Roxb. Proceedings of the Indian
Academy of Sciences B 15: 83 –105.
Refulio-RodriguezNF, Olmstead RG. 2014. Phylogeny of Lamiidae. American
Journal of Botany 101: 287– 299.
Reidt G, Leins P. 1994. Das Initialstadium der sympetalen Krone bei Sambucus
racemosa L. und Viburnum farreri Stearn. Botanische Jahrbu
¨cher fu
¨r
Systematik 116:1–9.
Rusby HH. 1897. The affinities of Dendrobangia Rusby. Bulletin of the Torrey
Botanical Club 24:79–81.
Santiago-Valentı
´n E, Viruet-Oquendo E. 2013. Notes on the flower, fruit, and
the reproductive phenology of the elusive Ottoschulzia rhodoxylon.
Harvard Papers in Botany 18: 61–65.
Sato
ˆY. 1971. Embryological study in Aucuba japonica Thunb., with special ref-
erence to the unusual development of the embryo sac. Science Reports,
To
ˆhoku University, Series IV (Biology) 35: 201– 206.
Sato
ˆY.1976. Embryological studies of some cornaceous plants. Science Reports,
To
ˆhoku University, Series IV (Biology) 37: 117– 130.
Scho
¨nenberger J, von Balthazar M, Sytsma KJ. 2010. Diversity and evolution
of floral structure among early diverging lineages in the Ericales.
Philosophical Transactions of the Royal Society B 365: 437–448.
Sleumer H. 1940. Beitra
¨ge zur Kenntnis der Icacinaceen und Peripterygiaceen.
Notizblatt des Botanischen Gartens und Museums Berlin-Dahlem 15: 228– 257.
Sleumer H. 1942. Icacinaceae. In: Engler A, Prantl K, eds. Die natu
¨rlichen
Pflanzenfamilien, 2nd edn, Vol. 20b. Leipzig: Engelmann, 322–396.
Sleumer H. 1971. Icacinaceae. In: van Steenis CGGJ, ed. Floral Malesiana,
Ser.I, Vol. 7. Leiden: Noordhoff, 1 –87.
Sogo A, Tobe H. 2006. Mode of pollen tube growth in pistils of Eucommia
ulmoides (Eucommiaceae, Garryales). International Journal of Plant
Sciences 167: 933– 941.
Endress & Rapini — Floral structure of EmmotumPage 14 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
Stevens PF. 2001 onward. Angiosperm phylogeny website, version 12 (July
2012). http://www.mobot.org/MOBOT/research/APweb [accessed 15
November 2013].
Stull GW, Refulio-Rodriguez NF, Olmstead RG, de Stefano RD, Soltis DE,
Soltis PS. 2014. Resolving enigmatic basal lamiid relationships with a
plastome-scale data set. Botanical Society of America, Botany 2014
abstract,www.2014.botanyconference.org/engine/search/index.php?func=
detail&aid=387.
Takhtajan A. 1997. Diversity and classification of flowering plants. New York:
Columbia University Press.
Takhtajan A. 2009. Flowering plants. Berlin: Springer.
Tang SH. 1962. Sporogenesis and gametophyte development in Eucommia
ulmoides Oliv. Acta Botanica Sinica 10: 29 –34.
Tobe H. 2012. Floral structure of Cardiopteris (Cardiopteridaceae) with special
emphasis on systematic and evolutionary implications. Journal of Plant
Research 125: 361– 369.
Tobe H. 2013. Floral morphology and structure of Phyllonoma
(Phyllonomaceae): systematic and evolutionary implications. Journal of
Plant Research 126: 709– 718.
Utteridge TMA. 2011. A revision of the genus Medusanthera (Stemonuraceae,
Icacinaceae s.l.). Kew Bulletin 66: 1– 31.
van Tieghem P. 1897. Sur les Phane
´rogames sans graines, formant la div-
ision des Inse
´mine
´es. Bulletin de la Socie
´te
´Botanique de France 44:
99–139.
von Balthazar M, Scho
¨nenberger J. 2013. Comparative floral structure and
systematics in the balsaminoid clade including Balsaminaceae,
Marcgraviaceae and Tetrameristaceae (Ericales). Botanical Journal of the
Linnean Society 173: 325– 386.
Zappi DC, Lucas E, Stannard BL, et al. 2003. Lista da plantas vasculares de
Catole
´s, Chapada Diamantina, Bahia, Brasil. Boletim de Bota
ˆnica da
Universidade de Sa
˜o Paulo 21: 345– 398.
Endress & Rapini — Floral structure of Emmotum Page 15 of 15
at Universitaet Zuerich on August 19, 2014http://aob.oxfordjournals.org/Downloaded from
