KEW BULLETIN VOL. 67: 751 – 758 (2012)
ISSN: 0075-5974 (print)
ISSN: 1874-933X (electronic)
Taxonomic dissolution of Sarcostemma (Apocynaceae:
Asclepiadoideae)
Ulrich Meve1 & Sigrid Liede-Schumann1
Summary. Since molecular analyses have demonstrated that Sarcostemma R. Br. is deeply nested in the predominantly Madagascan stem-succulent clade of Cynanchum L., the genus has been treated as a synonym of Cynanchum.
Some of the former Sarcostemma species have been transferred to Cynanchum in the course of various Flora treatments, and some new species belonging to this radiation have been described under Cynanchum. The present
contribution serves to complete the formal transfer of Sarcostemma taxa to Cynanchum, in which a total of nine
species are concerned: Cynanchum arabicum, C. areysianum, C. brevipedicellatum, C. daltonii, C. forskaolianum,
C. mulanjense, C. pearsonianum (a substitute name for Cynanchum pearsonii), C. sarcomedium (a substitute name for
C. intermedium), and C. socotranum. In addition, six subspecies of Cynanchum viminale are newly combined: C. viminale
subsp. australe, C. viminale subsp. brunonianum, C. viminale subsp. orangeanum, C. viminale subsp. stocksii, C. viminale
subsp. thunbergii and C. viminale subsp. welwitschii. Finally, notes on recent introductions from southern Yemen are
made, and illustrations of Cynanchum areysianum are provided.
Key Words. Cynanchum, Cynanchum areysianum, new combinations, Old World, taxonomy.
Introduction
The palaeotropical genus Sarcostemma R. Br. has long
been considered as a difficult group in ApocynaceaeAsclepiadoideae-Asclepiadeae. In consequence deviating perceptions are widespread in the taxonomic
literature (Liede & Meve 1992; Meve & Liede 1996;
Bruyns 2003, 2011; Goyder 2008). In the last 20 years,
the generic delimitation within Asclepiadeae saw
much phylogenetic enlightenment. Molecular studies
using cpDNA markers have convincingly refuted the
enlarged concept of Sarcostemma introduced by Holm
(1950), which was based mainly on morphological
similarities of corona structure. It has been shown that
neither Oxystelma R. Br., nor the American genera
Funastrum E. Fourn., Pentacyphus Schltr. and Philibertia
Kunth are congeneric with core Sarcostemma (Liede &
Täuber 2000). All these taxa constitute well circumscribed genera in their own right, occupying widely
divergent positions in the Asclepiadeae, so that their
corona similarities have to be interpreted as convergences (Meve & Liede 1999).
Both cpDNA and (nuclear) ITS data have shown
that Sarcostemma s.s., a group that accommodated
smooth, non-warty and non-striate succulents spread
over the Old World tropics, characterised by a ‘double’
corona of an outer ring and inner staminal corona
parts (as opposed to the ‘simple’ ring-shaped corona of
typical Cynanchum), is deeply nested in Cynanchum L.,
which would be paraphyletic if Sarcostemma was consid-
ered an independent genus (Liede & Kunze 2002;
Liede & Täuber 2002). Sarcostemma was demonstrated
to constitute a subclade of the large clade formed by all
Madagascan stem succulent Cynanchinae, including
the small genera Folotsia Costantin & Bois, Karimbolea
Desc. and Platykeleba N. E. Br. This clade, again,
constitutes the top clade of a Cynanchum clade consisting exclusively of Madagascan species. Meve & Liede
(2002) concluded that the African mainland must have
been originally colonised by Madagascan precursors of
Sarcostemma viminale (L.) L. It is, however, still unclear,
whether other regions of the distribution areas of
Sarcostemma taxa, e.g. India, have been reached via
mainland Africa (and Arabia), or independently and
directly from Madagascar by long distance dispersal,
and whether redistributions from these secondary areas
back to Madagascar have taken place as well.
Following these results, the other small succulent
genera have been merged with Cynanchum and their
species have been transferred formally to Cynanchum
by Liede & Meve (2001). However, for Sarcostemma,
only those species needed for Flora treatments have
hitherto been transferred to Cynanchum (Madagascar,
Liede & Meve (2001); tropical Africa, Goyder 2008).
A wide variety of commonly used molecular
markers has hitherto failed to produce any differences
between morphologically well distinguishable units in
Sarcostemma (Liede-Schumann, unpubl. results), leading to the conclusion that the genetic distances
Accepted for publication February 2012. Published online 6 September 2012
1
Department of Plant Systematics, University of Bayreuth, 95440 Bayreuth, Germany. e-mail: ulrich.meve@uni-bayreuth.de
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
752
between the different Sarcostemma taxa are extraordinarily low. For this reason, the traditional taxonomic
concept using morphological and karyological characters for taxon delimitation is followed to the present
day (cf. Liede & Meve 1989, 1992, 1993, 1995; Meve &
Liede 1996, 1997) and will also be applied here. Our
taxonomic work in Sarcostemma is based on the
concept that species are characterised by differences
in floral structure, whereas subspecies are characterised by differences at least in habit (Liede & Meve
1993). Following this concept, a number of circumscribable entities have been described as new taxa, the
last by Liede-Schumann & Meve (2005). The many
subspecies of Cynanchum viminale (L.) L. typically
represent ‘discernable natural groups’ which are often
identical with a specific ‘geotype’, e.g., a distinct
regional representative of the C. viminale complex
(cf. Liede & Meve 1993; Meve & Liede 1996; LiedeSchumann & Meve 2005). However, this concept is still
somewhat vague since recognition of the different
subspecific taxa needs some experience in that group.
Also, it is not possible to allocate a subspecific taxon
name to every collection of C. viminale s.l. Specimens
from western and central Africa are especially poor in
specific characters that would allow classification beyond attribution to C. viminale s.l. With the new
combinations proposed in the following, the genus
Sarcostemma ceases to exist as an accepted taxon.
New combinations
Cynanchum arabicum (Bruyns & P. I. Forst.) Meve &
Liede, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120418-1
Sarcostemma arabicum Bruyns & P. I. Forst., Edinburgh J.
Bot. 48: 333 (Bruyns & Forster 1991). Type: Saudi
Arabia, Hijila, 15 km E of Abha, Nasher IH 137
(holotype E).
Cynanchum areysianum (Bruyns) Meve & Liede, comb.
nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120419-1
Sarcostemma areysianum Bruyns, S. African J. Bot. 77: 802
(2011). Type: Yemen, Abyan Governorate, Jabal
Areys, 1,400 – 1,700 m alt., Jan. 2007, Bruyns 10287
(holotype B; isotype E).
NOTES. First counts of the chromosome number of
Cynanchum areysianum are here provided: 2n = 22.
Vouchers: YEMEN. Tawr al-Bahah, 13°11'N 44°18'E,
c. 250 m alt., 21 Nov. 2000, Lavranos, Mies & McCoy
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
KEW BULLETIN VOL. 67(4)
31335 (UBT); above Khadifut in the mountains of Ra’s
Fartaq, 15°39'N, 52°12'E, c. 150 m alt., 15 Nov. 2000,
Lavranos, Mies & McCoy 31313 (UBT).
For further remarks see below ‘Notes on novelties
from southern Yemen’.
Cynanchum brevipedicellatum (P. I. Forst.) Liede &
Meve, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120420-1
Sarcostemma brevipedicellatum P. I. Forst., Austral. Syst. Bot.
5: 59 (Forster 1992). Type: Australia, Queensland,
Gregory North Distr., Toko Tange, Glenormiston
Stn., Dec. 1982, Forster 1420 (holotype BRI; isotypes
AD, CANB, CBG, DNA, K!, MEL, PERTH, PRE,
QRS).
Cynanchum daltonii (Decne. ex Webb) Liede & Meve,
comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120421-1
Sarcostemma daltonii Decne. ex Webb, in Hook., Niger
Flora: 149, t. 14. (Hooker 1849). Type: Cape Verde
Islands, J. D. Hooker 1843 (lectotype K!, designated
here).
NOTES. This endemic of the Cape Verde Islands has
been placed as a synonym of Sarcostemma viminale
subsp. thunbergii (G. Don) Liede & Meve, a decision
influenced by the tetraploid genomes found for both
taxa (Liede & Meve 1993). However, we have since
investigated more material of the complex and realised
that S. daltonii should be separated from Cynanchum
viminale based on the unique character composition of
a non-twining, trailing to arching habit, long and short
laterals (peduncles; cf. Gonçalves 2002), and a chromosome number of 2n = 44. Regarding floral characters, C. daltonii is morphologically most close to C.
viminale subsp. viminale, though the follicles are much
stouter. Also, subsp. viminale always possesses a diploid
genome with 2n = 22 chromosomes (Liede & Meve
1995; Malla et al. 1978, Meve, unpubl. data).
Cynanchum forskaolianum (Schult.) Meve & Liede,
comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120422-1
Sarcostemma forskaolianum (as “forskålianum”) Schult. in
Roem. & Schult., Syst. Veg. (ed. 15) 6: 117 (Schultes
TAXONOMIC DISSOLUTION OF SARCOSTEMMA
1820). Type: Saudi Arabia, between Mudhaylif and
Mahayl on the Jeddah-Gizan road, 500 ft., Collenette
1977 (neotype K!, designated by Meve & Liede
(1996)).
753
name Sarcostemma pearsonii, under which this species
has started to become a well-known taxon within the
last 20 years.
Cynanchum sarcomedium Meve & Liede, nom. nov.
Cynanchum mulanjense (Liede & Meve) Liede & Meve,
stat. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120423-1
Sarcostemma mulanjense Liede & Meve, Novon 2: 223
(1992). Type: Malawi, Mulanje (Mt), outer slopes at
the Chitakale stream, west branch, Chapman &
Chapman 6892 (holotype MO!).
Cynanchum viminale (L.) L. subsp. mulanjense (Liede &
Meve) Goyder (2008: 417).
NOTES. Goyder (2008) considered Cynanchum mulanjense a subspecies of C. viminale. Applying the concept of
species and subspecies as outlined above, namely, using
variation in floral morphology as a criterion of species
delimitation, C. mulanjense deserves specific status. It is
characterised by nodding flowers, narrow, slightly
twisted creamy petals and an elongated gynostegium,
although the latter character breaks down in central
and northern Malawi (cf. Goyder 2008). With this
character combination, C. mulanjense seems to be more
closely related to C. oresbium (Bruyns) Goyder than to C.
viminale. These two species share both floral similarities
and a preference for similar habitats, rocky outcrops in
Malawi and Mozambique, respectively.
Cynanchum pearsonianum Liede & Meve, nom. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120425-1
Sarcostemma intermedium Decne., in DC., Prodr. 8: 538
(Decaisne 1844), non Cynanchum intermedium N. E.
Br. (Brown 1908: 747). Type: India ([‘Peninsula
Ind. orientalis’]), Herb. Wight 1556 (holotype P, not
traced; isotype G-DC! (2 sheets)).
NOTES. Medium-thick stems, small and acute corona
lobes and an elongated style-head make this species
readily distinguished from the other representatives of
the Cynanchum viminale relationship in India. But since
N. E. Brown (1908) used the name Cynanchum
intermedium for a leafy South African twiner (of an
uncertain status), a replacement name for Sarcostemma
intermedium in Cynanchum became necesssary, and the
name Cynanchum sarcomedium is proposed here.
Cynanchum socotranum (Lavranos) Meve & Liede,
comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120426-1
Sarcostemma socotranum Lavranos, Natl. Cact. Succ. J. 27
(2): 37 (1972). Type: Yemen, Socotra, Hama-di-roh,
on vertical limestone faces, c. 350 m alt., April 1967,
Smith & Lavranos 309 (holotype K!).
http://www.ipni.org/urn:lsid:ipni.org:names:77120424-1
Sarcostemma pearsonii N. E. Br., Bull. Misc. Inform., Kew
1913: 301 (Brown 1913), non Cynanchum pearsonii
N. E. Br. (Brown 1914: 18). Type: Namibia, Great
Karasberg, on stony plains SW of Krai Kloof,
1,600 m alt., 19 Jan. 1913, Pearson 8460 (holotype
K!; isotype BOL!).
NOTES. Sarcostemma pearsonii, a species that is confined
to very dry and stony habitats in Namibia and NW
South Africa, was neglected for a long time, although its
erect, shrubby habit and the small and twisted corolla
lobes make it one of the most easiest species to identify
(Liede & Meve 1989). Brown (1914) assigned the name
Cynanchum pearsonii to a shrubby species with small
leaves, which is nowadays treated as a synonym of
Cynanchum meyeri (Decne.) Schltr. (Liede 1993).
The necessary nomen novum proposed here,
tries to resemble as much as possible that of the
Cynanchum viminale (L.) L. (Linnaeus 1771: 392)
subsp. viminale
NOTES. The protologue of Cynanchum viminale refers to
an illustration of a plant from Egypt (Felfel Tavil) as the
type and states explicitly ‘Habitat in Africae maritimis’.
However, Indian taxa such as Sarcostemma acidum (Roxb.)
Voigt and S. brevistigma Wight & Arn. were synonymised
under S. viminale subsp. viminale by Ali (1983), based on
material from Pakistan. Later, this synonymy has been
adopted by Jagtap & Singh (1999) for India. Other
regional Floras, such as the Flora of China and the Flora of
Nepal (www.eFloras.org) have not followed this usage and
recognised S. acidum and S. brevistigma as separate
species. The present authors follow the view of Ali
(1983) and consider these two species as synoynyms of C.
viminale subsp. viminale, thus extending the area of the
latter from West Africa and Egypt to India.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
754
Cynanchum viminale (L.) L. subsp. australe (R. Br.)
Meve & Liede, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120428-1
Sarcostemma australe R. Br., Prodr.: 463 (Brown 1810).
Type: Australia, South Australia, Bird Island, Petral
Bay, Isle St. Francis, 3 Feb. 1802, R. Brown (Iter
Australiense 2872) (lectotype BM!, designated by
Forster (1992)).
Sarcostemma viminale subsp. australe (R. Br.) P. I. Forst.,
Austral. Syst. Bot. 5: 64 (Forster 1992).
Cynanchum viminale (L.) L. subsp. brunonianum
(Wight & Arn.) Meve & Liede, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120429-1
Sarcostemma brunonianum Wight & Arn., in Wight,
Contr. Bot. India: 59 (1834). Type: India, [‘Peninsula
Ind. orientalis’], Cody Cally, village of Autcherroccum, Herb. Wight 1557 (lectotype G-DC! (No.
G00301010), designated here; isolectotypes E, GDC! (No. G00136527)).
Sarcostemma viminale (L.) R. Br. subsp. brunonianum
(Wight & Arn.) P. I. Forst. (Forster 1992: 63).
Cynanchum viminale (L.) L. subsp. orangeanum (Liede
& Meve) Liede & Meve, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120430-1
Sarcostemma viminale subsp. orangeanum Liede & Meve,
Bot. J. Linn. Soc. 112: 70 (1993). Type: South Africa,
Northern Cape, 11.4 km E Kuruman, Liede & Meve
579 (holotype K!; isotype MSUN!).
Cynanchum viminale (L.) L. subsp. stocksii (Hook. f.)
Meve & Liede, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120431-1
Sarcostemma stocksii Hook. f., Fl. Brit. India 4: 27 (Hooker
1883). Type: Pakistan, Sind, Stocks 509 (holotype K!).
Sarcostemma viminale subsp. stocksii (Hook. f.) Ali (1983:
31).
NOTES. This subspecies seems to be indistinguishable from Cynanchum viminale subsp. viminale except
for the stouter follicles that are much more divaricate and taper only insignificantly towards base and
apex. The seeds are also thicker, and wingless, dark
brown and rugulose (cf. Liede 2002: 235). A very
good illustration of the type of Sarcostemma stocksii is
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
KEW BULLETIN VOL. 67(4)
available: Hooker (1852, plate 861), published
under ‘S. brachystigma’, an erroneous name for S.
brevistigma, now a synonym of C. viminale subsp.
viminale (http://www.bio.uni-bayreuth.de/psysl/
hooker/hooker.php?pg=0861).
Cynanchum viminale (L.) L. subsp. thunbergii (G. Don)
Liede & Meve, comb. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120432-1
Sarcostemma thunbergii G. Don, Gen. Hist. 4: 156
(1838). Type: South Africa, Cape Province,
Worcester, Karoo Botanic Garden, Bayer 68 (neotype NBG!, designated by Liede & Meve (1993).
Sarcostemma viminale subsp. thunbergii (G. Don) Liede
& Meve (1993: 10).
Cynanchum viminale (L.) L. subsp. welwitschii (Hiern)
Liede & Meve, comb. et stat. nov.
http://www.ipni.org/urn:lsid:ipni.org:names:77120433-1
Sarcostemma welwitschii Hiern, Cat. Afr. Pl. 1: 689 (1898).
Type: Angola, Huilla, base of Morro de Lopollo,
Welwitsch 4261 (holotype BM!; isotypes BR!, C).
NOTES . This element described from southern
Angola is still quite poorly known, though, undoubtedly, it is a member of the Cynanchum
viminale complex that extends into Namibia. It is a
remarkably glabrous, vigorously tangling scrambler
and climber, which can produce voluminous plants.
The inflorescences are mostly lateral and sessile,
rarely on short laterals (peduncles) or terminal. The
most conspicuous character seems to be the rather
low number (two to five) of flowers per inflorescence.
C. viminale subsp. welwitschii is a tetraploid with a
chromosome number of 2n = 44, as the single count
available suggests, obtained from material from
northernmost Namibia (Voucher: Ruacana, Albers et
al. 3617, UBT). With its polyploidy, subsp. welwitschii
is distinguished from C. viminale subsp. stipitaceum
(Forssk.) Meve & Liede and subsp. viminale, the taxa
otherwise having most similarities with subsp. welwitschii.
From the other tetraploid taxon of southern Africa, C.
viminale subsp. thunbergii, C. viminale subsp. welwitschii differs in habit, and in stems that are thinner,
softer and green instead of grey-green.
Figueiredo & Smith (2009) included two taxa in
their list of succulents of Angola; Sarcostemma welwitschii
Hiern and S. viminale subsp. viminale. These authors
neither mention the second Angolan taxon described
by Hiern, S. andongense Hiern, nor S. viminale subsp.
stipitaceum into which Liede-Schumann & Meve (2005)
TAXONOMIC DISSOLUTION OF SARCOSTEMMA
have sunk S. andongense. More material, especially living
plants, from Angola and adjacent regions need to be
studied before a final taxonomic conclusion can be
made.
Notes on novelties from southern Yemen
A floristic inventory by J. Lavranos, T. McCoy and B.
Mies in southern Yemen in November 2000 yielded
some additional morphological variants of stem-succulent Cynanchum of the Sarcostemma subgroup. Four
living cuttings taken during this excursion were
transferred into cultivation in the greenhouse of the
Department of Plant Systematics, University of Bayreuth. All four accessions flowered in the following
years. One accession from near Lawdar (Lavranos,
McCoy & Mies 31372, UBT) was found to represent a
rose- to white-flowered form of Cynanchum viminale
subsp. stipitaceum (Fig. 1A), another one from Ra’s
Fartaq (Lavranos, McCoy & Mies 31363, UBT) is
755
vegetatively similar to subsp. stipitaceum, florally a
mixture of this subspecies and C. areysianum or
C. arabicum (Fig. 1B), but possesses a reddish to redcoloured corolla. It could represent a natural hybrid.
Hybrids, however, are rare in Cynanchum, and molecular analysis to support this assumption has yet to be
done. Finally, two accessions, one from Tawr al-Bahah
(Lavranos, Mies & McCoy 31335, UBT), and one from
above Khadifut in the mountains of Ra’s Fartaq
(Lavranos, Mies & McCoy 31313, UBT), are vegetatively
comparable to C. arabicum, but florally similar to the
Socotran endemic C. socotranum (Figs 1B – E, 2). For
this element we therefore prepared a new species
description but later had to recall it from the
manuscript when Bruyns (2011) described Sarcostemma
areysianum, which exactly matches our new species. In
addition to the brief differential diagnosis given by
Bruyns (2011) we made further observations on the
status of the three closely related taxa C. arabicum, C.
areysianum and C. socotranum: Vegetatively, C. areysianum
Fig. 1. A Cynanchum viminale subsp. stipitaceum, Yemen; B Cynanchum areysianum (left) together with Cynanchum arabicum,
Yemen (right); C Cynanchum areysianum; D shoots of Cynanchum areysianum, C. socotranum and C. arabicum (from left to right);
E Cynanchum socotranum. A from Lavranos et al. 31372; B from Lavranos et al. 31313 (left), Radcliffe-Smith & Henchie 4624
(right); C from Lavranos et al. 31335; D from Lavranos et al. 31335 (left), Mies et al. 1503 (middle), Radcliffe-Smith & Henchie
4624 (right); E from Mies et al. 1503 (all in UBT). PHOTOS: ULRICH MEVE.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
756
KEW BULLETIN VOL. 67(4)
Fig. 2. Cynanchum areysianum. A flower bud; B flower in lateral view, with two petals removed; C gynostegium and corona, with
parts of corona removed; D pollinarium; E style-head, with one pollinarium in natural position. All from Lavranos, Mies & McCoy
31335 (UBT). DRAWN BY ULRICH MEVE.
cannot be directly distinguished from C. arabicum,
with its erect to arching (non-twining), thick (usually
6 – 7 mm diam.), greyish green and stout stems
(Fig. 1D). Usually the stems and especially the nodes
of C. areysianum are even thicker than in C. arabicum
and additionally equipped with a corky ring; the
internodes are mostly shorter (cf. Fig. 1D). C. areysianum therefore is really a stout plant totally different in
habit from the delicate C. socotranum, whose stems are
around 2.5 – 3.5 (– 4) mm thick and often constricted
at the nodes (Fig. 1D, central shoot). Flowers in C.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
areysianum appear terminally or on short lateral
peduncles (Fig. 1B, top, 1 C), as can be seen in most
plants of C. arabicum, whereas the flowers in C.
socotranum normally appear laterally in a (sub)sessile
manner (Fig. 1E). With C. socotranum, however, C.
areysianum shares the rather small flowers with membraneous, oblong, suberect to erect corolla lobes,
although the flowers are a bit larger and the corolla
lobes are much more twisted as in C. socotranum, and
also creamish brown to rose instead of greenish yellow.
Other shared features include the thickish, rounded
TAXONOMIC DISSOLUTION OF SARCOSTEMMA
and more or less erect staminal corona lobes. However,
in contrast to C. socotranum the corona lobes are
inflated, uneven and much surpassing the style-head
(Fig. 2C). All three species lack a complete outer
coronal ring formed by interstaminal and (outer)
staminal parts as found in most other ‘Sarcostemma’
taxa. Instead, the ‘ring’ is not continuous and broken
into ‘five plus five’ separated fringes or scales. Very
significant for C. areysianum, one mostly lobular and
emarginate scale is fused to the basal back of each
staminal corona lobe (cf. Fig. 2B). This corona
structure is unique in Cynanchum. In addition, the
staminal corona lobes are of very delicate tissue and
inflated. They are also larger, as in the two related
species, and of an uneven surface and irregular outline.
Furthermore, they cover and greatly exceed the
conspicuously large, massive and strictly conical stylehead (Fig. 2E). Details of the gynostegium look very
similar to those found in C. socotranum, although it is
larger: the gynostegium is clearly higher than broad
(but as high and as broad as in C. arabicum, cf. Bruyns &
Forster 1991: Fig. 1E), the guide rails are strictly pointed
(not forming a ‘mouth’ as in C. arabicum), and the
fleshy base of the gynostegium leaves considerable
open space beneath the guide rail entrance (whereas
the mouth/base of each guide rail is directly fused to
the gynostegium without leaving an open space beneath in C. arabicum). In contrast to both species, the
anther appendages are much longer than wide, triangular-lanceolate and rather acute, while they are
triangular-deltate and more or less as long as wide in
C. socotranum and C. arabicum. Finally, the style-head
(Fig. 2E) is larger and higher than in the two related
species, whereas the style itself is elongated up to
0.8 mm in length (not shown in Fig. 2), and reminiscent
of C. socotranum. In C. arabicum the style is considerably
shorter. C. areysianum indeed shares a number of
significant features, especially of the flowers, with C.
socotranum, which is therefore clearly identified as its
sister-species.
Acknowledgements
We are very grateful to John J. Lavranos and Dr Bruno
Mies, who provided us with living plant material from
southern Yemen, and to G for scanning type specimens of C. Wright.
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Sigrid Liede-Schumann