During this study, the present author examined 3157 herbarium collections from 39 herbaria from (physical or digital) loans or in situ (B, BM, BR, BRI, C, CANB, CBG, COI, DSM, EA, FR, FT, G, GAT, GOET, H, HBG, HEID, JE, K, L, LISC, LISU, M, MO, MSB, NHT, P, PERTH, PR, PRC, S, U, UBT, UPS, W, WAG, Z, ZT). Additional collections were obtained via personal communication (BO, DNA, TUB, US), from web pages such as like JStor Plant Science (JPS, http://plants.jstor.org/), Chinese Virtual Herbarium (CVH, http://www.cvh.org.cn/), and homepages of the following herbaria: A, AAU, BAR, CAY, FLAS, FSU, FTG, GH, HAST, NTUF, NY, PDA, TAIF, and USF. New collections were added if the photograph allowed identification or if misidentification appeared to be unlikely (esp. C. grandis collections from the Pacific area), while duplicates were added without visual inspection of the specimen photo. Online availability of specimen images is mentioned in the list of exsiccatae (Suppl. material 1). Ten species were cultivated in greenhouses of Munich Botanical Garden: C. abyssinica (Lam.) Cogn. (1 origin, 4 individuals), C. adoensis var. jeffreyana (1 origin, 4 individuals), C. grandiflora Cogn. (1 origin, 1 individual), C. grandis (3 origins with 2, 61, 3 individuals, respectively), C. hirtella Cogn. (1 origin, 12 individuals), C. megarrhiza C.Jeffrey (1 origin, 8 individuals), C. microphylla Gilg (2 origins, 2 and 1 individual, respectively), C. rehmannii Cogn. with two varieties (2 origins, each 3 individuals), C. sessilifolia (Sond.) Cogn. var. sessilifolia (1 origin, 8 individuals), and C. trilobata (Cogn.) C.Jeffrey (2 origins, each 3 individuals). The present author performed crossing experiments among eight of these species. Morphological features were documented photographically and in the form of vouchers, with 47 collections deposited in M. Field data were obtained on a trip to NE Tanzania in 2009 resulting in 28 Coccinia collections.

For this monograph the phylogenetic data of Holstein and Renner (2011a; 2011b) were augmented with 20 new sequences from 8 accessions (GenBank accession numbers are given in Suppl. material 2), and new phylogenies were calculated using RAxML v. 7.2.6 (Stamatakis 2006) and MrBayes v. 3.2 (Ronquist et al. 2012). The substitution model was GTR+Γ as used before, and 1000 ML replicates were used to infer statistical support for the nodes via bootstrapping. For Bayesian analysis, four chains were run with 2,000,000 generations, with a sampling frequency of 1000. The first 25% of the trees were discarded as burn-in, and the rest were plotted as a 50% majority rule consensus tree using FigTree 1.3.1 (http://tree.bio.ed.ac.uk/software/figtree/). Gaps in the plastid matrix occurring in more than one accession were coded as “0”, “1”, or “?”, with “?” when data were missing or when shorter gaps were coded in the same place, but in different accessions.

Of the examined collections, 2024 were geo-referenced and mapped in Google Earth (Google Inc., Mountain View, CA, USA). Cultivated plants were geo-referenced according to the original collection site. If collecting sites were given as distances from locations, a path along major roads was used, beginning from the center of the starting location. Collecting sites were geo-referenced according to the description even if coordinates were given on the label, except for cases in which the coordinates were clearly derived from GPS or if the description did not allow further improvement. Location names were cross-validated from printed maps and then imported into DIVA-GIS 7.1.6.2 (http://www.diva-gis.org). If collecting sites of specimens appeared to be too useful to ignore in the distribution maps despite the large uncertainty of the position (radius > 5 km) or if the collecting site was only given as “nearby” a distinct locality, then geo-referenced coordinates are given in brackets. Political administrative borders were taken from GADM v.1 (Jan 2009) or v.2 (Jan 2012) (http://www.gadm.org/) and elevation data (1 km resolution) from CGIAR Consortium for Spatial Information (Jarvis et al. 2008). The geodetic datum for the maps is WGS84; the projection in each case is equirectangular. Coordinates are given in decimal degrees in Suppl. material 1 with WGS84 as geodetic datum.

Coccinia species are perennial climbers or creepers. The lignification of the mature shoots differs among the species from unlignified to completely lignified. Climbing is enabled by tendrils, which are either simple or bifid. Tendril development in young plants is delayed and emerges in C. abyssinica after the 6^th node (Getahun 1974a). The tendril arms are only rarely equally sized, as one is usually much smaller; true dichotomy of tendrils is unknown from Coccinia. Whether a species has simple or bifid tendrils is often not fixed, but there is a strong predominance of one kind. Bifid tendrils regularly occur or are predominant in C. grandiflora Cogn., C. heterophylla (Hook.f.) Holstein, C. hirtella Cogn., C. intermedia Holstein, C. mackenii Naudin ex C.Huber, C. mildbraedii Gilg, C. racemiflora Keraudren, C. schliebenii Harms, and in some forms of C. barteri (Holstein and Renner 2011b). Strikingly, Coccinia species with bifid tendrils occur in rather humid habitats. This suggests an adaptive advantage, because more tendril arms increase stability, as the leaves of rainforest species are larger, coriaceous, and thus heavier than leaves of species from drier habitats. Some species are regularly described as having simple tendrils in floristic treatments, but they may bare bifid tendrils such as C. sessilifolia (N. Holstein 13) and C. senensis (H.J.E. Schlieben 5745 in B, K, and MO). Coccinia adoensis has bifid tendrils even in some type specimens (e.g., G.H.W. Schimper 166 in BR8886781 and on the sheet with a drawing in K) and is still listed as simple-tendrilled. All three species with this polymorphism, however, have predominantly simple tendrils. Interestingly, these species are also closely related to species with predominantly bifid tendrils: C. sessilifolia with C. hirtella and C. mackenii, and C. adoensis with C. grandiflora and C. schliebenii.

Coccinia species have perennial roots. Most (if not all) species are woody at the base, and most of them produce hypocotyl tubers (Fig. 1a). Some species, such as Coccinia adoensis and C. grandiflora (and most likely also C. senensis (Klotzsch) Cogn. and C. schliebenii), however, produce globular subterranean root tubers, much like potatoes, but smaller in size (Holstein and Renner 2011b; Zimmermann 1922b; pers. observ.). Root tubers in Coccinia adoensis are likely to be an adaptation to fire, as this species predominantly occurs in woodlands. In contrast to rather mild fires in semi-arid savannas with less inflammable biomass, woodland fires produce temperature rises of 60 °C in 0–3 cm depth (Bradstock and Auld 1995; Gignoux et al. 1997), so vegetative buds near the ground (hemicryptophytes) might be damaged, whereas root tubers (geophytes) have a higher chance of survival.

Figure 1. 

a Young plant of C. grandis. The hypocotyl is already thickened and lignifies later-on to a tuber. The cotyledons are glabrous, have an entire margin and an obtuse apex b Adventitious root on C. grandis; the beige structure to the left is a dry tendril.

Coccinia grandis and C. barteri produce adventitious roots if stems touch the soil (Fig. 1b). Coccinia hirtella, C. sessilifolia and their F1 hybrids with C. grandis appear to lack this ability (pers. observ.). Adventitious roots also occur along the hypocotyl of C. abyssinica seedlings (Getahun 1974a). There is barely any research on root anatomy, solely Getahun (1974a) reports tetrarch vascular bundles in the primary roots of C. abyssinica seedlings and di- to triarch bundles in secondary roots.

Many species, such as C. abyssinica, C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. rehmannii, C. sessilifolia, and C. trilobata, produce a lignified tuber that is derived from the hypocotyl (Zimmermann 1922b; pers. observ., Fig. 1a). The tuber, at least of some species, contains starch as a storage nutrient (Getahun 1974b). It develops during the first season, and lignification may begin as soon as the appearance of the first tendrils, such as in C. abyssinica (N. Holstein 132). Some species, such as C. adoensis and C. grandiflora (and most likely also C. senensis and C. schliebenii) do not produce hypocotyl tubers but root tubers. In C. adoensis var. jeffreyana the hypocotyl is minute (N. Holstein 130), which prevents the development of a tuber. Whether West and Central African forest species produce tubers is unknown.

Each plant produces one to several shoots, which can persist or die back completely during the dry season or due to fire or grazing. Coccinia microphylla shoots can lignify completely and produce short green branches with flowers and small leaves during the dry season (Fig. 2a), whereas shoots of C. sessilifolia do not lignify at all (pers. observ. from greenhouse cultivation over 4 years). The shoots of C. grandis can become slightly succulent. The length of the shoots varies from 70 cm in C. microphylla to 20 m in C. grandiflora and C. mildbraedii. Zimmermann (1922a) reports a stem of C. grandiflora being 6 cm in diameter. Usually, the bark of the hypocotyl tuber and the shoots is grayish in color. Fresh shoots and twigs are usually deep green to brownish green, sometimes speckled with pale to whitish pustules. In C. abyssinica and C. megarrhiza the shoots and tendrils can turn purple during maturity. Coccinia sessilifolia produces glaucous shoots that bear a waxy bloom (Fig. 2b). The indumentum of Coccinia species, if present, is composed of simple, oligo- to multicellular eglandular trichomes up to 2 mm in length. The long trichomes consist of oblong cells that may appear articulate when dried (Fig. 3a). Shorter trichomes can be lineal to conical (Fig. 3b). Sometimes, trichomes have a thickened base that appear warty when the trichomes break off. The density of the trichomes is often increased on the nodes. Trichome type and length on shoots are like those of the abaxial surface of the petioles, but usually less dense. Young shoots often exhibit short (< 0.5 mm), weak trichomes, even in species that are later glabrous, e.g., in C. grandis or C. sessilifolia. Glandular trichomes are rare, few-celled, not visible with the naked eye and have been found, e.g., in C. grandiflora and C. grandis (pers. observ.; Thanki 1989; Fig. 3c). Glandular trichomes are also observed in young stems of C. abyssinica (Getahun 1974a), which are usually covered with long multicellular eglandular trichomes.

Figure 2. 

a Female flower bud of C. microphylla (N. Holstein et al. 90); picture taken during the dry season. The stem is completely lignified, and only green short shoots are produced b Male plant of C. sessilifolia. The stem is glaucous and does not lignify. Unusually, the bract is 3-lobate leaf-like.

Figure 3. 

Trichomes on Coccinia species. a Node of C. adoensis var. jeffreyana (J.C. Lovett 1197). The black bar equals 1 mm. b Part of a leaf C. adoensis var. jeffreyana (A.F. Stolz 504). The white bar equals 1 mm. c Glandular trichome from C. grandis.

Zimmermann (1922b) reports epigeous cotyledons for C. grandiflora and C. grandis, of which the latter is confirmed by personal observations (Fig. 1a). Epigeous cotyledons also occur in C. abyssinica, C. adoensis var. jeffreyana, C. microphylla, C. rehmannii aff. var. littoralis, and C. sessilifolia. The hypocotyl and cotyledons of all observed taxa are glabrous. The cotyledons are elliptical to obovate and have an entire margin. The cotyledons are slightly fleshy and green, which is also observed in those of C. abyssinica (Getahun 1974a), and the cotyledonous apex has a pale marking and is obtuse to retuse. Getahun reports that the prominent veins and the margins on the lower cotyledon surface in C. abyssinica are covered with multicellular trichomes. However, prominent veins in C. abyssinica cotyledons cannot be confirmed, and if multicellular trichomes occur, then they are not visible to the naked eye. The first normal leaf in this species, however, emerges in the axilla of the cotyledons (N. Holstein 132, Fig. 4a), and thus might have been confused.

Figure 4. 

a Young plant of C. abyssinica (N. Holstein 132). The first node is in the axilla where the glabrous cotyledons split off. The first nodes lack probracts and tendrils b Young plant of C. sessilifolia (N. Holstein 131). The first leaves in this species are petiolate, sessile leaves are produced later-on. The glabrous cotyledons are already dried (plant had the same age as the one in Fig. 4a).

The leaves of Coccinia species are simple, alternate, and paired with a tendril on each node, except for the first nodes (Figs 1a, 4a, b). Leaves of all species are petiolate, except for C. sessilifolia var. sessilifolia, which only develops petioles when young (N. Holstein 131, Fig. 4b) or rarely subsessile leaves when older; full petioles in this species are only realized in C. sessilifolia var. variifolia (A.Meeuse) Holstein. Subsessile leaves are common in C. quinqueloba and C. senensis, while the other species’ leaves are usually distinctly petiolate. The petioles’ surface can be glabrous, at maturity speckled with hyaline to white cell clusters (C. grandis, C. heterophylla, C. intermedia, C. quinqueloba, C. rehmannii, C. samburuensis, C. senensis, C. subsessiliflora), or have an indumentum. The petiole contains several vascular bundles arranged in a U-shape (Fig. 5a). However, Hussain et al. (2011) report a ring of vascular bundles in C. grandis. The adaxial side of the petiole often bears two ridges above the “lateral” vascular bundles (Fig. 5a). These ridges merge into the leaf margin and usually bear trichomes (Figs 3b, 5b, c). The abaxial side of the petiole shares its indumentum with the lower leaf lamina, at least at the base of the veins (Fig. 5c).

Figure 5. 

a Cross-section of a petiole of C. grandiflora, stained with astra blue and safranin (3:2). The bicollateral vascular bundles are arranged in a U-shape b Trichome on the adaxial ridge of a cross-section of a petiole of C. grandiflora. Although not visible by naked-eye, the petiole is also covered with few-celled glandular trichomes c Young plant of C. adoensis var. jeffreyana. The trichomes are mainly occurring on the prominent veins. The adaxial side of the petiole bears smaller trichomes on the ridges, which fade into the leaf margin.

The venation in C. grandis is reticulate, and the mid rib is reported to contain three bicollateral vascular bundles with xylem and phloem arranged in a ring (Hussain et al. 2011). Reticulate venation can be confirmed for all Coccinia species except C. ogadensis, in which only the central vein in each lobe is visible.

Young leaf buds often bear a dense indumentum, even in species that are glabrous at maturity, e.g., in C. grandis. The leaf lobes are linear, elliptic, (ob-)ovate to triangular. The incision depth of the lobes can be consistent (C. ogadensis, C. subsessiliflora) or highly variable (C. adoensis, C. grandis, C. senensis (Fig. 6)), even within a single individual. In taxa with a variable degree of lobation, young leaves tend to be not or shallowly lobed (e.g., C. grandis, C. megarrhiza, C. rehmannii aff. var. littoralis, C. sessilifolia), a differentiation according to light exposure might also be possible. The leaf margin usually is beset conspicuously with small teeth and often bears trichomes (Figs 3b, 5b, c), even in otherwise glabrous species (e.g., C. grandis, C. sessilifolia). The teeth are at the apex of lobes, lobules and smaller orders of serration or situated along the entire margin. The term “dentate” (toothed) is therefore ambiguous in literature describing Coccinia, as it might also refer to the margin morphology (Stearn 2004). The teeth are often pale, but can also be colored, esp. when dry, such as in C. abyssinica, C. grandis, C. intermedia, C. longicarpa, C. megarrhiza, and C. samburuensis (Fig. 7a). The coloration of teeth is inconspicuous in young plants and develops during maturation (as observed in C. abyssinica, C. grandis, and C. megarrhiza). The teeth are interpreted as hydathodes by Zimmermann (1922a), because he observed water drops in C. grandis and C. trilobata on the teeth of the 2^nd order (except those of the tip of the lobes) in the morning. A white deposit at the teeth on the upper side of the leaf of a C. adoensis plant (P. Quarré 75; PR) seems to support Zimmermann’s interpretation.

Figure 6. 

Leaf shape variability in Coccinia senensis. aH.J. Schlieben 5259 (HBG) bE.M.C. Groenendijk et al. 1031 (WAG) cA.R. Torre et al. 18788 (MO). Black bars equal 1 cm.

The upper leaf lamina is often covered with transparent to white pustules, that contain cystoliths (Avetta 1894; Solereder 1899; Zimmermann 1922a; pers. observ.). The pustules consist of up to 25 cells in C. mackenii (Avetta 1894) but are larger and denser in glabrous species from dry habitats (esp. C. ogadensis). As they develop over time (they are smaller and less well visible in forest species), it can be assumed that the pustules are an adaptation towards protection against high solar radiation. When acetic acid is applied to microscopic sections of the leaves, heavy gas development suggests that the cystoliths consist of CaCO₃ (pers. observ.). This can be observed in C. grandis, C. hirtella, and C. sessilifolia, hence also when the pustules are not conspicuous as in the latter two species. The pustules may form the base of small trichomes, such as in C. adoensis var. jeffreyana (Fig. 3b) or C. microphylla. In some species, the upper surface is usually covered with an indumentum (C. hirtella, C. schliebenii, C. senensis, and C. trilobata), but it may also be reduced, and other species rarely exhibit a trichome-bearing upper surface, e.g., C. adoensis. In each case, the trichomes are simple, < 1 mm, and whitish. The veins on the upper surface are either glabrous to the naked eye or are covered with small < 0.5 mm long simple trichomes. Zimmermann (1922a) observed in C. grandis that the glabrous surface of the lamina is only slightly wettable, whereas a drop of eosine disperses along the veins rapidly. Zimmermann argues that these “capillary drainage lines” might serve to transport water to the hydathodes during the dry season.

The lower leaf lamina is paler than the upper side (Fig. 3b) and can be glabrous or bear an indumentum. The highest density of the indumentum can be found on the prominent veins (Fig. 5c). The indumentum on the lower leaf surface and the abaxial surface of the petiole can consist of eglandular oligo- to multicellular trichomes. The trichomes are appressed or upright (Fig. 5c), usually filiform, sometimes also narrowly conical (e.g., C. abyssinica). Filiform trichomes are straight, curved, or sinuate. Long filiform trichomes often appear articulate when dry due to sunken lateral cell walls (Fig. 3a). Dry trichomes are hyaline, whitish, beige, or yellowish. The lower lamina often displays deeply colored to dark green to blackish extranuptial glands (Fig. 7b). The glands usually occur at the base of the leaf between the veins, sometimes also between secondary ramifications (C. grandis) or along the main veins (C. grandiflora). The epidermis of the lower leaf lamina in C. grandis consists of cells with undulating anticlinal cell walls and anomocytic stomata (pers. observ.).

Figure 7. 

a Male flower of C. grandis (N. Holstein 37). Apices of the petals and calyx lobes, as well as major teeth on the leaf margin are colored in red. Minor margin teeth are inconspicuously colored. The calyx lobes in C. grandis are spreading in flower buds and reflexed in mature flowers b Male plant of C. sessilifolia. Darkish glands (extranuptial nectaries) are commonly found at the base of a lower leaf lamina. The calyx lobes are unusually large in this specimen (cp. Fig. 2b).

In addition to the foliose leaves, most Coccinia species have bracteose prophylls on sterile nodes, which are called “probracts” (Zimmermann 1922b). The probracts can be up to 5 mm long, but also rather small (< 1 mm) or caducous. The first nodes of the seedling lack probracts, and they are developed on later nodes. The shape of the probracts is ovate and entire with a round to acute apex. They are often spoon-like presenting the lower surface (e.g., C. adoensis, C. barteri, C. grandis, C. megarrhiza, C. sessilifolia; Figs 3a, 8b), or they are folded in the middle with a prominent keel (C. grandiflora; Fig. 8a). Probracts can be glabrous or bear short (< 1 mm) trichomes, and bear extranuptial glands on the lower surface (Fig. 8a; Okoli and Onofeghara 1984).

Figure 8. 

a The probract of C. grandiflora is fleshy and has a keel. The abaxial side bears many extranuptial nectaries. The structure pointing to the lower left of the picture is the tendril b The probract of C. trilobata (sampled as N. Holstein & P. Sebastian 9) is spoon-shaped, papery, and without a keel.

Bracts (leaves subtending inflorescences or flowers), if present, look like the probracts. Bracts below inflorescences are as large as probracts, while bracts below flowers tend to be smaller. Bracts can be present or absent, the latter being an indicative character for some species.

In rare cases, probracts and bracts can be leaf-like (e.g., N. Holstein 126, Fig. 2b; P.C.M. Jansen 2065; H. Wanntorp & H.E. Wanntorp 1159) indicating that the (pro-)bracts are likely derived from usual leaves.

The conspicuous glands on the lower leaf surface, probracts, and bracts (Figs 7b, 8a) are of the Benincasa-type (sensu Zimmermann 1932), meaning that they are flat and consist of several layers of secretory cells, which are surrounded by a single-layered sheath (Muhammad Ilyas 1992; Okoli and Onofeghara 1984; pers. observ.). This sheath is lignified in C. microphylla and C. trilobata (Zimmermann 1922b). However, Zimmermann (1932) cites Nieuwenhuis von Üxküll-Güldenbandt as saying that the sheath in C. grandis is suberinized, but the present author did not find such a statement in the citations given in that paper (eventually, this was a personal communication). Schrödter (1926), however, finds that young sheaths in Luffa aegyptiaca are lignified but become suberinized with age, so the difference might be explained by different stages. Chakravarty (1948) interprets the sheath as filter tissue that is surrounded by an “external osmotic tissue”. Also Muhammad Ilyas (1992) interprets these radially elongated cells as secretory and notes that they have a connection to the vascular strand. However, Okoli and Onofeghara (1984) find that the glands in C. barteri are too distant to be interpreted as vascularized. Zimmermann (1922b) observes intermediate forms between few-celled, stalked glandular hairs and the Benincasa-type glands in C. microphylla and C. trilobata, including the sheath that forms the base of the protruding glandular tissue. The glands secrete a clear, rarely slightly colored, sweet-tasting exudate (pers. observ. in C. grandiflora and C. grandis). In C. grandis the exudates contain sucrose, glucose, fructose, alanine, tryptophane, threonine, and an unidentified amino acid (Muhammad Ilyas 1992).

Male flowers mostly occur in racemes that are usually accompanied by 1–2 solitary flowers on the same node (Fig. 2b). The first flowers in male plants of C. hirtella, C. rehmannii, and C. sessilifolia are solitary. Racemes appear later in the course of the flowering season, although racemes are generally rare in the first species (pers. observ.). If solitary flowers and racemes are produced on the same node, then the solitary flower(s) precede(s) those of the racemes in time of maturity (Fig. 2b). The trigger to produce racemes instead of or additionally to solitary flowers is not known. The racemes bear up to 35 flowers (e.g., in C. pwaniensis, C. racemiflora). Within the racemes, flowering starts at the basalmost branches. If the peduncle is reduced, flowers appear clustered on the node. In C. grandis, which usually produces single flowers only, flower clusters (short-peduncled racemes) rarely occur. This can be seen in plants from Ethiopia, Saudi Arabia but also from India and Sri Lanka. The pedicels of solitary male flowers of C. hirtella, C. megarrhiza, and C. rehmannii exhibit a negative gravitropism. In creeping plants, pedicels that grow downwards in the beginning make a sharp bent upwards to present the flower upright.

Female flowers are mostly solitary. Only in some species, female flowers are usually in racemes, such as in C. heterophylla, C. keayana, and C. racemiflora. Few-flowered female racemes or clustered flowers might also occur in C. grandiflora, C. intermedia, and C. subsessiliflora. In C. barteri, female flowers can be solitary or in few- or many-flowered racemes. Two female flowers per node have also been observed in C. microphylla. The pedicels of solitary female flowers are negatively gravitropic during flower development. After pollination, the pedicels of solitary female flowers of C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. rehmannii, and C. sessilifolia exhibit positive gravitropism. The downturn is not due to slackness caused by the weight of the developing fruit but an active process, as the pedicels thicken and remain firm. However, only fertilized flowers turn downwards completely, as aborted flowers from mispollination never reach this state (pers. observ. in cultivated plants).

The perianth of all Coccinia species is synsepalous and sympetalous. At the base, calyx tube and corolla tube are connected with each other and form a perianth tube or funnel. Depending on the exsertion point of the staminodes in female flowers, parts of the tube form a hypanthium (e.g., C. grandiflora).

The calyx differentiates as a bulge (Fig. 7a, b) with usually five lobes, or only the lobes emerge from the perianth tube (Fig. 9). If the calyx emerges as a bulge, then it and the perianth tube are rather conspicuously differentiated from the corolla in terms of color. If only the calyx lobes emerge, then the color of perianth tube fades to green color towards the receptacle, with the veins of the corolla remaining more intensely colored. Whether calyx and corolla are non-differentiated (congenital fusion) or postgenitally fused, is not known for Coccinia, but in the distantly related Echinopepon wrightii (A.Gray) S.Watson the perianth tube is non-differentiated (Leins and Galle 1971). The outside of the perianth tube can bear long trichomes of the type on as the lower leaf surface or the petioles (Fig. 10a). The calyx lobes are acute triangular to subulate or linear, rarely slightly lanceolate. The orientation of the calyx lobes is erect, spreading, or reflexed, although they can be curved inwards (e.g., C. rehmannii aff. var. littoralis (Fig. 10a) or outwards (e.g., C. intermedia). The color of the calyx lobes can be more intense (green) than the perianth tube or the pedicel (Fig. 7b). In C. grandis, the tip of the calyx lobes is brownish to reddish just as the teeth on the leaves and the corolla (Fig. 7a).

Figure 9. 

Leaky dioecy in a plant of C. megarrhiza. The plant was flowering male (the bud on the left) through the season, but a single female flower developed (the second flower on this node was male). The flower was receptive and produced a normal-sized fruit and normal-shaped seeds. The probracts (left node) are spoon-shaped, the tendrils are purplish.

Figure 10. 

a Male plant of C. rehmannii [aff. var. littoralis] (N. Holstein 126). The plant was raised from seeds of a female plant with ovoid fruits (B. Jarret – pers. comm.) b Male flower of C. adoensis var. aurantiaca (N. Holstein et al. 85). The halictid bee (H. Schaefer – pers. comm.) circled around the globose anther head harvesting pollen. The scent of the flower was strong and honey melon-like.

The petals of Coccinia species are fused at the base, usually for at least one third of the total length. Rarely, the petals are free down to the height of the calyx lobes (pers. observ. in C. megarrhiza, C. rehmannii var. rehmannii, and C. sessilifolia). Perianth tube and corolla tube are often campanulate, rarely funnel-shaped or tubular. The perianth tube can be urceolate in C. longicarpa, C. racemiflora and sometimes in C. barteri. The tips of the (4–)5(–7) corolla lobes are rounded to acute with an apical tooth. The apical tooth can be inconspicuous or colored claret red or brown, such as in C. adoensis var. aurantica or C. grandis. Outside, the perianth tube and the corolla is glabrous or covered with short (< 10 globose cells in C. grandis) trichomes. Inside, the corolla is covered with long trichomes (up to 20 cells in C. grandis), sometimes with a glandular apical cell (Fig. 10b). The trichomes become shorter towards the receptacle. The inner side of the hypanthium of female flowers is glabrous and smooth, which suggests nectary tissue, in C. grandiflora, C. grandis, and C. hirtella (Fig. 11a). The size of the corolla does not differ conspicuously between staminate and pistillate flowers; pistillate flowers might be a bit smaller.

Figure 11. 

a Longitudinal section of a female C. hirtella flower (size of the small squares is 1 mm²). Perianth and style were detached. The pollen sacs on the staminodes are highly reduced. The introrse side of the staminodes bears long trichomes that in intact flowers touched the style b Female flower of C. rehmannii var. rehmannii with bilobate stigma arms c Female flower of C. megarrhiza with bulging stigma arms.

In staminate flowers, the three stamens originate from the base of the perianth tube, and the filaments are fused to a central column (Fig. 10a). The fusion point sometimes leaves a small gap to the hollow receptacle center. This gap, however, can be filled with long multi-cellular trichomes (e.g., in C. abyssinica and C. megarrhiza). Rarely, the filaments can also be separate. The filaments are glabrous and white, greenish, yellowish, or orange. The number of vascular bundles in the stamens is disputed. Chakravarty (1954) reports five vascular bundles in C. grandis: two stamens have two bundles each, and the third stamen has a single bundle. Later research shows three vascular bundles for the same species with one per stamen (Bhuskute et al. 1986; Deshpande et al. 1986). In C. hirtella each stamen contains a single vascular bundle (pers. observ.).

The anthers together form a globose head (Fig. 10b). Each anther is bithecate; sometimes one can be monothecate (Bhuskute et al. 1986; Chakravarty 1954). Each theca is sinuate. Deshpande et al. (1986) report a bi-layered fibrous endothecium and a secretory tapetum, which they found differs from distantly related Momordica charantia L.

In pistillate flowers, the three, now free, stamens are reduced to staminodes that originate from the interior perianth wall, forming a hypanthium. Introrsely, the staminodes of C. grandiflora, C. grandis and C. hirtella bear long, multicellular trichomes, except for the apex, extrorsely the staminodes are glabrous (Fig. 11a). The anthers of the staminodes are strongly reduced to a slightly yellowish spot at the apex in C. grandis and C. hirtella. The staminodes of C. megarrhiza bear long multicellular trichomes introrsely and laterally but are glabrous extrorsely.

Pollen in Coccinia species shows little diversity. The pollen is oblate-spheroidal to prolate with a reticulate exine (Table 1). Additionally, the pollen of C. pwaniensis (Holstein and Renner 2010), C. hirtella, and C. trilobata is prolate, the exine texture is unknown. The sampling of the examined species covers all clades and suggests uniformity in shape and exine texture, which negates systematic value of pollen in Coccinia. The color is yellow in C. abyssinica, C. grandiflora (Zimmermann 1922b; and pers. observ.), C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. rehmannii, C. sessilifolia, and C. trilobata, and orange in C. adoensis var. aurantiaca. Zimmermann (1922b) reports that pollenkitt of C. grandiflora contains a yellow colorant that is soluble in peanut oil, but not in water and only slightly in heated chloral hydrate solution. It changes its color in concentrated sulfuric acid to blue, in Lugol’s iodine (I₂KI) to green, and in osmic acid to brown. As in several other cucurbit species, in vitro germination of C. grandis pollen increases from pH = 7 towards alkalinity and is maximal at pH = 8.5 (Zaman 2009).

Pistillate flowers are epigynous and have three (rarely two or four) carpels. The ovary is narrowly spindle-shaped, oblong to globose. The surface is smooth or warty; it is glabrous or has the indumentum of the pedicel. The style is often greenish-white or pale-yellowish; the stigmas are frequently in yellowish colors and covered with long trichomes (Fig. 11c). Each stigma in C. grandiflora, C. grandis, C. hirtella, C. megarrhiza, C. rehmannii, and C. sessilifolia is U-shaped with the ends of the lower sides of the arms touching each other. The stigmatic branches can be long and free, such as in C. grandiflora, C. grandis and C. rehmannii var. rehmannii (Fig. 11b), or short and bulbous, such as in C. hirtella, C. megarrhiza (Fig. 11c), C. microphylla, and C. sessilifolia.

The placentation of the ovules in Coccinia is involute, which is also discussed for other Cucurbitaceae by Leins and Galle (1971). The funicle appears to be attached to the outer wall, but actually attaches to a septum coming from the axis (Fig. 11a, b, c), which itself is connected to the outer wall. The axis-wall septum, however, might be reduced during ripening, but this needs further study.

The anatomy of the ovules is barely surveyed in Coccinia. In C. abyssinica and C. grandis, the ovules are reported to be anatropous, bitegmic, and crassinucellate (Getahun 1973; Zahur 1962). Anatropus ovules also occur in C. hirtella (Fig. 12a). The position of the ovules is horizontal in C. grandis (Kirkwood 1904), C. hirtella (Fig. 12a), and C. megarrhiza (Fig. 12b) with the micropyle facing outwards. Horizontal ovules are regularly reported in the Benincaseae and the Cucurbiteae (Schaefer and Renner 2011a).

In staminate flowers, a pistil is not developed because the stamens fuse to a central column. The pedicel is narrow and reaches the perianth, and there is no indication of even a thin (sterile) inferior ovary in the flower.

Figure 12. 

a Cross-section through an ovary of C. hirtella. The ovules are anatropous with the micropyle facing outwards b Cross- and longitudinal section of a C. megarrhiza fruit. The seeds are enclosed in a hyaline hull (aril) and seemingly attached to the periphery c Cross-section through a fruit of C. sessilifolia. Note that the vascular bundles in the lower left of the picture bend in the periphery, so the placentation is not parietal but involute.

The development of the embryo has only been investigated in C. grandis. Chakravorti (1947) and Zahur (1962) report that the female gametophyte development is according to the Polygonum-type. Both observe that the synergides possess hooks instead of the filiform apparatus. Chakravorti (1947) describes the developing endosperm as a nuclear type, which is confirmed by Chopra (1955). By formation of a large central vacuole, the nuclei become displaced to the periphery. After the endosperm becomes cellular, the often lateral chalazal haustorium remains coenocytic. Then, the haustorium becomes cellular with multinuclear cells except for the apex (Chopra 1955).

The fruits are many-seeded berries, which vary in size and shape between species (and within C. grandis, C. rehmannii, and C. subsessiliflora). The smallest fruits occur in C. rehmannii var. rehmannii and C. microphylla with globose berries as small as 1 cm in diameter at maturity. However, in both species larger globose fruits (up to 2.5 cm in diam.) and in C. rehmannii ovoid fruits may occur additionally, in the latter case especially in more humid habitats. The largest fruits occur in C. samburuensis and the rainforest species C. grandiflora, C. longicarpa, C. mildbraedii, and C. schliebenii, which have long elliptical to cylindrical (sausage-shaped) fruits up to 20 cm long and up to 5 cm in diameter.

Immature fruits often have a white or pale-green (C. hirtella, C. sessilifolia) or dark green (C. adoensis) longitudinal mottling or lines, even when the ovary and the ripe fruit is single-colored (Figs 2a, 13a, b, c). In the C. rehmannii clade, the white spots or lines become surrounded by a dark green halo during ripening (Fig. 13c). Rarely, if no white mottling develops, e.g., in some C. microphylla, dark green spots develop nevertheless. In any case, the mature fruit in species of the C. rehmannii clade is usually uniformly colored red (Zimmermann 1922b; and pers. observ.). Ripening usually occurs from green with or without mottling via yellow to orange to the final coloration. The color changes from the apex of the fruit downwards (Fig. 13a, b, c), independent of the position (hanging vs. horizontal) in C. sessilifolia. In C. megarrhiza, pendulous fruits ripen from the apex to the base, which sometimes remains green even when the apex already turns soft. In lying fruits from creeping C. megarrhiza plants, ripening does not proceed from the apex, but starts from point that is closest to the source of either warmth or light (pers. observ. from greenhouse cultivation). The degree of the yellow to orange ripening zone varies. In C. sessilifolia, fruits directly turn red, whereas in C. grandis the color change includes a well visible yellow zone. Unripe fruits collected of C. grandis tend to turn yellow outside and pink to red inside (Imbumi 2004). Mature fruits are in deep red colors (hence the genus name) or orange-red. Rarely, a white longitudinal mottling is described in ripe fruits (e.g., C. mackenii).

Figure 13. 

a Ripening fruit of C. hirtella. Note the typical lobulate leaves of this species in the lower right b Ripening fruit of C. sessilifolia. The fruit, like the plant, bears a waxy bloom c Ripening fruits of C. megarrhiza have a dark green halo around the white longitudinal mottling. The left fruit is derived from pollination with C. megarrhiza pollen, whereas the smaller fruit on the right is derived from cross-pollination with C. trilobata (both pollinations were conducted on the same day).

Immature fruits are glabrous or have the same indumentum as the ovary. By ripening, the indumentum is usually reduced. The exocarp of Coccinia fruits is papery thin and has a waxy bloom when ripe. The endo- and mesocarp are red, fleshy and soft (Fig. 12b, c). The pulp is nerved with a dense network of tubular tissue. Shah et al. (1983) report that such a network consists of sieve tubes in C. grandis. The sieve tubes are not connected to the main vascular strands and are filled with a proteinaceous material. The authors suggest that the sieve tube network aids nutrient transport during the rapid growth of the fruit.

The seeds (Fig. 14) in Coccinia species are beige to grayish with a small margin, which often has a darker coloration. The shape is more (esp. in the C. rehmannii clade) or less asymmetrically ovate (especially C. adoensis, C. pwaniensis, and C. senensis). The surface is flat, esp. in the C. rehmannii clade, to lenticular (esp. C. adoensis, C. pwaniensis, and C. senensis). The size varies from 4.5–7 × 3–5 × 1–2 mm (L/W/H). Seed numbers per fruit vary drastically from about 10 (C. microphylla) to c. 100 (+ c. 20 infertile) in C. sessilifolia (N. Holstein 119). Species with larger fruits might contain more seeds.

Figure 14. 

Seeds of Coccinia. The lack of fibers in e and f are preparation artifacts due to mechanical removal of the hyaline aril. Maceration (coarse crushing of the fruit and soaking of the mass in water for 2–3 weeks; R. Brüggemann – pers. comm.) retains the surface fibers. Length of white bars equals 1 mm. a Seeds of C. adoensis var. jeffreyana (plant derived from seed of the same fruit: N. Holstein 130). Note the lenticular face and symmetrical shape of the seed b seeds of C. abyssinica (plant derived from seed of the same fruit: N. Holstein 120 and 132) c Seeds of C. trilobata d Seeds of C. sessilifolia (harvested by maceration) e Seeds of C. sessilifolia (harvested by mechanical extraction; taken from N. Holstein 119) f Seeds of C. grandis (harvested by mechanical extraction).

Detailed observations of the seed anatomy have been made by Getahun (1973) for C. abyssinica and by Chakravorti (1947) for C. grandis. Getahun describes the mature seed as consisting of the embryo, a membrane-like structure (pellicle) closely adhering the embryo but separated from the hard testa. However, Chakravorti does not recognize a pellicle in C. grandis. Both authors agree that the inner integument disappears and the testa develops solely from the outer integument. The testa of C. abyssinica is described as comprising four layers (from center outwards): (1) a thin-walled parenchyma, (2) a sclerenchyma of macrosclereids, (3) a thick-walled parenchyma, and (4) an epidermal layer. The outermost layer, the epidermis, is disintegrated, leaving the cell walls as slender rods of 500 µm length. This has also been noticed in other species, and the surface has been described as a fibrillose testa (Jeffrey 1967; Kéraudren 1967). De Wilde et al. (2011) also interpret the seed surface of C. grandis as having a disintegrated, pulpy, radiately striate exotesta.

Getahun contrasts his observations with those of Chakravorti (1947) in C. grandis, but the seeds are in fact similar, just incompletely described by Chakravorti. Chakravorti draws a four-layered testa, but does not name the innermost layer that has the same hatching as the third layer, which he describes as “cells with thickened walls”. This is what Getahun calls parenchyma. Chakravorti’s outermost layer, the epidermis, consists of radially elongated cells with thin walls. These cells have likely just not yet disintegrated as observed by Getahun. The only difference between both observations is the second layer, which consists of macrosclereids in C. abyssinica and of radially slightly elongated cells with thin walls in C. grandis. These different observations are explainable by two possibilities: 1) different developmental stages of the seeds, since Chakravorti surveys the seed development, so the layers are immature, while Getahun surveys mature seeds and germination, or 2) different staining. Chakravorti uses haematoxylin alone, which does not stain lignified cell walls, whereas Getahun uses haematoxylin with safranin as counter stain, which makes lignin, and thus sclerenchyma, well visible (von Aufseß 1973).

The seeds in Coccinia, at least in C. abyssinica (Hora 1995), C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. mildbraedii, C. sessilifolia, and C. subsessiliflora (pers. observ.) are surrounded by a hyaline red juicy envelope (Fig. 12b). As the ovule is bitegmic (see above), one might assume the hyaline envelope is the testa. Chakravorti (1947), however, observes that the juicy envelope is derived from carpellary tissue. However, Getahun (1973) does not recognize the hyaline hull in C. abyssinica, which is surprising as it also occurs in the closely related species C. megarrhiza and C. microphylla. Similar structures to the hyaline hull are also found in other Cucurbitaceae, esp. in Momordica. Van der Pijl (1982) interprets these as “endocarp-pulpa” taking over the function of an aril for seed dispersal as the fruits of Momordica species dehisce at maturity. However, Coccinia fruits disintegrate and do not dehisce, e.g., into valves.

The seeds of C. abyssinica maintain a high germination rate (100%) after four years of storage at room temperature (Getahun 1973). However, time from watering until germinating increases from 4 days (after one year of storage) to 16 days (after four years of storage). Seeds of C. grandis are also able to germinate after four years of storage, while seeds of C. ogadensis Thulin (3 seeds tested) did not germinate after five years (pers. observ.). Getahun (1973) reports that C. abyssinica seeds do not germinate below 10 °C and above 35 °C. In the latter case, he observes thermal damage to hypocotyls and primary roots. The optimum for germination in C. abyssinica is between 20 and 30 °C and that of C. grandis is 35 °C, whereas temperatures < 23.5 °C and > 40 °C inhibit germination (Li et al. 2001). The germination rate of C. abyssinica seeds in the light is decreased by 35% compared to germination in darkness (Getahun 1973). In C. sessilifolia, seed viability declines after 9 months, and germination is at a maximum after 10–20 min smoke exposure or red:far red light treatment, followed by burying and a long-day cycle (Weiersbye and Witkowski 2003). Rotting of a crushed ripe fruit in water (for seed extraction) resulted in germination of two seeds in an artificial hybrid (C. megarrhiza ♀× C. rehmannii aff. var. littoralis ♂) after 3 weeks of soaking (pers. observ.). Coccinia grandis seeds do not exhibit dormancy (Motooka et al. 2003); for the other species there is no information available.

Coccinia is one of the few examples in the plant kingdom, in which at least one species has heteromorphic sex chromosomes (Ming et al. 2011). Coccinia grandis contains 22 autosomes plus 2 gonosomes. Female individuals have homomorphic XX, whereas male individuals have heteromorphic XY chromosomes (Fig. 15a). Although Kumar and Deodikar (1940) report males to have two large “X” and females a large X and a smaller Y chromosome, later studies (Chakravorti 1948; Kumar and Vishveshwaraiah 1952) reveal that males are heteromorphic and the Y is 2.5 (Bhaduri and Bose 1947) to 3–4 times longer (Guha et al. 2004) than the other chromosomes. Some years before Kumar and Deodikar, Sutaria (1936) reported n = 12 from pollen mother cells of C. grandis, without finding the large Y chromosome. Although scientists from India conducted some research for C. grandis, chromosome work in other Coccinia species is almost none-existent. McKay (1930) reports n = 12 for C. hirtella, without mentioning whether he studied a male or a female individual. The author’s own chromosome counts (Table 2; Fig. 15b) support McKay’s report and reject the existence of heteromorphic sex chromosome in C. hirtella males. This is also the case for C. sessilifolia (Fig. 15c). Two counts in the C. rehmannii clade reveal a reduction of chromosome number and the non-existence of a heteromorphic Y chromosome there.

Figure 15. 

Chromosome preparations fixed in 3:1 EtOH – acetic acid and stained with orcein, objective lens: 100×. a Mitotic plate of a male C. grandis (2n = 22 + XY) b Mitotic plate of a male plant of C. hirtella (2n = 24) c Phase contrast image of a mitotic plate of a male plant of C. sessilifolia (2n = 24).

Due to the sex chromosomes, sex expression in C. grandis plants is pre-determined and sex ratios in the offspring basically follow Mendelian inheritance of a single allele. However, Agarwal and Roy (1983) report that of 500 planted seeds only 181 (36.2%) were male, and their interpretation is that there might be a genetic mechanism to reduce the number of male plants. As they do not report XY females, their finding might be explained rather by an increased lethality of XY embryos due to deleterious mutations on the single X or on the Y in Y-containing pollen. The Y chromosome in C. grandis is dominant, as the presence of a single Y results in male phenotypes, regardless of the number of X chromosomes (Agarwal and Roy 1975; Kumar and Vishveshwaraiah 1952; Roy and Roy 1971b). Triploids of C. grandis with a 3n = XYY constitution are also male but bear flowers in clusters instead of the usually solitary ones and exhibit leaf deformations (Roy and Roy 1971b).

Evidence for Mendelian inheritance of sex in C. hirtella is not so clear, as the same plant can produce flowers of the opposite sex in succeeding seasons. Two plants marked as female and one as male from observation of flowers produced flowers of the opposite sex in the following year (pers. observ.), making C. hirtella functionally dioecious, but genetically hermaphroditic. On the other hand, there are several observations of flowers of the opposite sex in otherwise unisexual plants. Kumar and Vishveshwaraiah (1952) report a gynodioecious form of C. grandis that has homomorphic chromosomes (XX). Although bisexual flowers are reported to develop, pollen grain development is arrested, and the male function remains suppressed. Roy and Saran (1990), however, report fully fertile hermaphroditic flowers in an otherwise female individual. Holstein and Renner (2011a) report a collection of C. intermedia that bears male floral buds and female flowers and young fruits on the same nodes. This observation can be interpreted as ‘leaky dioecy’ (Baker and Cox 1984). Among the author’s own cultivated plants, a male individual of C. megarrhiza produced a single female flower towards the end of the season (Fig. 9). Although two male flowers on the same individual were open at the same time when the female flower was mature, the pollen sacs did not open. It is not known whether this was a coincidence or functionally significant, e.g., to prevent selfing. Selfing is often discussed as being advantageous in small population sizes, e.g., when new islands are colonized. Prevention of simultaneous flowering of both sexes on the same plant implies that leaky dioecy would not immediately aid the establishment of new distant populations per se. It might require the establishment of several plants or clonal separation. In any case, the single female flower was receptive and was fertilized by another male C. megarrhiza plant derived from the same fruit as the “female” plant. The resulting fruit and seeds developed normally.

The production of hermaphroditic flowers in X-radiation studies (Agarwal and Roy 1983; Roy 1974) shows that dicliny in Coccinia is kept up actively. Agarwal and Roy found hermaphroditic flowers on two plants with otherwise female flowers and an XX configuration. They also report the development of a normal fruit without mentioning the fertility of pollen from hermaphroditic flowers, but interpret their finding as cleistogamy. However, fruit development without previous pollination (parthenogenesis) or from pseudogamy with pollen from different genera as fructification stimulus is described by Lal (1973). True selfing from own pollen (in irradiated XX individuals) would mean that the Y chromosome is not important for fertile pollen development. Furthermore, this means that it only carries at least one gene for suppression of the development of the female organs, and the occurrence of a second X suppresses pollen development in “normal” plants. Agarwal and Roy (1983) also report that X-ray dosages of 5 to 50 R [1.29 × 10^-3 to 12.9 × 10^-3 C/kg] result in a drastic reduction of the sex ratio (11 males, 2 hermaphrodites, and 127 females out of 500 irradiated seeds). This might indicate that the single X bears many functionally important genes in contrast to the Y, as mutations in the single X lead to an increased mortality compared to females with a balancing second X chromosome.

Aside from research on the sex chromosomes, a few studies on the genome of C. grandis have been undertaken. Guha et al. (2004) report the 4C nuclear DNA content of female C. grandis as 8.37 ± 0.14 pg, whereas that of male C. grandis is 10.17 ± 0.24 pg. This means that the difference between X and Y chromosome adds about 20% to the complete DNA content. Patankar et al. (1985) report a DNA content of 1C = 2.75 pg for C. grandis, however, they do not report the sex of the analyzed individual. Interphase nuclear structure in C. grandis is chromocentric with 14 ± 0.25 chromocenters (Patankar et al. 1985).

Surveys on the reassociation kinetics in Cucurbitaceae suggest that C. grandis has the lowest amount of repetitive DNA among the six species studied in the Cucurbitaceae (Bhave et al. 1984). Fragments of 550 bp length have 25% of repetitive elements (Bhave et al. 1984), whereas 7400 bp long fragments consist of 49% repetitive DNA (Bhave et al. 1986). However, Pasha and Sen (1995) report different results as they find 400–600 bp long fragments to comprise 38% highly repetitive DNA (52% total repetitive DNA), which appears to be average in the Cucurbitaceae. Pasha and Sen do not discuss this difference, which cannot be explained by difference in sex, as the large amounts of plant material used (1 kg seeds or 100 seeds respectively) suggest that it must have comprised elements of both sexes. A sex discriminating study of C. grandis reassociation kinetics has not been undertaken yet.

Charles Naudin’s famous work on the effects of hybridization included crosses between Coccinia plants. He reports successful crosses between Asian C. indica (nom. illeg. for C. grandis) and the NE African C. schimperi (P06809214, P06809215, P06809216; Naudin 1862), which is now seen as a synonym of C. grandis. Naudin’s Coccinia schimperi, however, has buff petals, whereas the Asian C. grandis has snow-white petals. Both supposed species hybridized without problems. During the following two years, Naudin could not intercross within the F1 generation because plants of different sexes did not flower at the same time, so he crossed F1 individuals with a female C. grandis from Asia, which again produced offspring. As Naudin erroneously supposed that he dealt with two species, he deduced that hybrids between species could be fully fertile, have a reduced fertility or be sterile, and that there was no clear boundary between species and varieties. However, he proved rather that the buff-petaled, African C. schimperi and the white-petaled Asian C. grandis are a single species obeying the biological species concept.

Naudin also crossed other Coccinia species that he had in cultivation. Coccinia quinqueloba and C. mackenii, although sometimes not easily distinguishable, were not amenable to crossing (Naudin 1866). Only 1 out of 20 crossing trials resulted in a fruit that developed poorly. Naudin did not publish whether the hybrid seeds were fertile or even viable, but his observations are valuable as each one accession of C. quinqueloba and C. mackenii were not distinguishable using more than 3500 bp of plastid sequences, and hence might share the same plastid haplotype (Holstein and Renner 2011b). There are collections that share characters of C. mackenii and C. quinqueloba, but these are not intermediates. In these collections, long petioles (typical for C. mackenii) are coupled with simple tendrils (typical for C. quinqueloba), and thus cannot be unambiguously allocated to either species. However, if both typical forms are indeed reproductively isolated, then they are species sensu Mayr (1942), and the crossing behavior of these species needs to be tested reciprocally to define the morphological scope of the two species.

Naudin also crossed male C. diversifolia (C. abyssinica) with a female C. mackenii, which are rather distantly related and do not co-occur in nature. However, the cross resulted in onset of mediocre fruits with only few, but well-developed and viable seeds (Naudin 1866). Naudin did not report further results for this cross either.

As reproductive isolation between species is often assumed but rarely tested, crossing experiments among species that are cultivated in Munich Botanical Garden have been performed. Positive results are given in Table 3.

Figure 16. 

Hybrids of Coccinia species. a Coccinia grandis ♀ × C. hirtella ♂ b Coccinia hirtella ♀ × C. grandis ♂ c Coccinia grandis ♀ × C. pwaniensis ♂; note that the pollen sacs are not open although the flower is in full bloom indicating sterility d Left flower: male C. sessilifolia, right flower: male flower of C. grandis ♀ × C. sessilifolia ♂ (C. grandis flowers are about equally sized as C. sessilifolia).

Interspecific fertilization succeeded or failed without correlation of relatedness or co-occurrence (Table 4). Female flowers of C. sessilifolia could not be fertilized with pollen of C. megarrhiza (4 trials), C. trilobata (4 trials), C. rehmannii (2 trials), C. hirtella (3 trials) or Diplocyclos palmatus (2 trials). Pollinated female flowers were discarded like non-fertilized flowers. Hence, hybridization seems to be prevented prezygotically in female C. sessilifolia with members of the C. rehmannii clade and C. hirtella as pollen donor. As C. sessilifolia and C. rehmannii co-occur widely in their range and share flowering time and floral syndrome, the production of hybrids would reduce fitness drastically. Coccinia sessilifolia and C. hirtella do not co-occur, but belong to the same clade (see chapter Evolution and phylogeny). Although a female C. sessilifolia could not be fertilized by pollen from C. hirtella, pollination of a female C. hirtella with pollen from C. sessilifolia resulted in fruit onset.

In contrast to C. sessilifolia, C. grandis is fertilized easily by C. hirtella and C. sessilifolia, although the species neither co-occur, nor are closely related. The cross resulted in offspring, which was growing vigorously but sterile, as pollen sacs did not open (Table 3). Hybrid pollen that was extracted from the pollen sacs of fully open flowers was also not able to fertilize C. sessilifolia (1 trial). The occurrence of sex chromosomes in C. grandis might result in gene dosage imbalance, which interferes with the floral development, leading to sterile offspring. The inability of female C. grandis to be fertilized by C. rehmannii aff. var. littoralis and C. trilobata (Table 4) might be explained by the fact that the chromosome numbers differ (see Table 2) and translocations lead to gene loss in hybrid genomes and thus inviability of the offspring. On the other hand, the cross between female C. hirtella and male C. trilobata (not sympatric) produced a purely intermediate F1 generation, which flowers vigorously despite the difference in chromosome numbers (see Table 2 and 3). Although the anthers open like in fertile flowers, unlike in C. grandis hybrids, the pollen of this hybrid was not able to fertilize female flowers of C. hirtella (1 trial), C. grandis (2 trials), or C. sessilifolia (2 trials).

Roy and Roy (1971a) report an intergeneric cross between a female C. grandis and a male individual of the monoecious Diplocyclos palmatus, resulting in a morphologically intermediate F1 offspring in 5% of the trials. All F1 individuals are female, indicating that the X chromosome bears at least one gene for maleness suppression, which is dominant over the maleness genes of D. palmatus. Whether the F1 is fertile, is not clear, as the authors report successful back-crossing only with a female [sic, male?] C. grandis but not with D. palmatus. To the author’s knowledge, there are no reports of the F2 generation. However, if the parental sexes were the other way around (male C. grandis × female D. palmatus), fertilization was not possible.

Although bee pollination is observed for only a few species, most Coccinia species exhibit characters that support a general attraction to bees. The petal color is commonly pale yellow but can also range to white, pale pink or bright orange, with green, yellow, orange to purple venation. Anthesis is during the day in C. abyssinica, C. adoensis var. aurantiaca, C. grandiflora, C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. rehmannii, C. sessilifolia, and C. trilobata (pers. observ.) but often only for a few hours (in, e.g., C. megarrhiza, C. rehmannii). Zimmermann (1922b) reports pollen release in C. grandiflora at 6.30 a.m. before blooming of the flower, opening of the flower between 7 and 8 a.m. and wilting after noon. Ash (J.W. Ash 898) reports flower opening a.m. in C. schliebenii. Anthesis time in the other Coccinia species is not reported, but also likely to happen during the day. The scent is rather weak and dull sweetish, resembling that of honey melon, in C. abyssinica, C. grandiflora, C. hirtella, C. rehmannii, C. sessilifolia, and C. trilobata, weak but fresh in C. grandis, and intense, sweet, and fruit-like (like honey melon) in C. adoensis var. aurantiaca and C. megarrhiza. The only evidence of an alternative to bee pollination is C. ogadensis, which is reported to smell of rotten meat (P. Ellis 163 and 383). However, it is unclear whether the flowers emit a fetid scent or whether the smell comes from crushed vegetative parts, as it is known from Momordica foetida or Kedrostis foetidissima (Jacq.) Cogn. (Jeffrey 1967).

Bee pollination is confirmed for C. rehmannii (C.J. Ward 12250), C. adoensis var. aurantiaca (Fig. 10b), C. grandiflora, and C. grandis. Observed pollinators of C. grandis are Trigona apicalis Smith, 1857 and Trigona collina Smith, 1857 in Thailand (Jongjitvimol and Wattanachaiyingcharoen 2006), and Megachile sp. in Cambodia (H. Schaefer, pers. comm.). The present author observed a halictid bee (Fig. 10b; identification by H. Schaefer, pers. comm.) in a male C. adoensis var. aurantiaca walking on the globose anther head and collecting pollen in the corbicula. Stigmas in Coccinia are lobed (Fig. 11b) or bulging (Fig. 11c), and nectaries are located presumably in the hypanthium, so one can assume stripping of the pollen from the venter when crawling into the flower. Zimmermann (1922b) also observed the circling around the anther head in the large-flowered C. grandiflora. He identified the visiting small bee as Trigona sp. He also noted that a bee just having visited a Momordica flower walked on the inner side of the corolla loading dorsally located pollen on the anthers of a male C. grandiflora flower.

There are no observations of actual seed dispersal but mammals and birds appear to be attracted by the fruits and likely act as seed dispersers. Fruit bats such as Cynopterus sphinx (Vahl, 1797) feed on C. grandis fruits in Thailand (Elangovan et al. 2001; Ruby et al. 2000). Fruits of C. grandis are also taken up by birds (Bhatt and Kumar 2001) and eaten by humans (Voigt 1845). Elephants also feed on C. grandis (Mubalama 2000) and are possibly also seed dispersers. From its introduction to Pacific Islands, dispersal of C. grandis by humans is well-known (Muniappan et al. 2009). Human dispersal, in many cases likely to be intentional (Starr et al. 2010), also explains the occurrence of this species in the Neotropics and even in Missouri, USA. Some occurrences in Australia can also be explained by escape from gardens. Zimmermann reports feeding on C. grandiflora fruits by birds, small mammals but also snails and beetles (Zimmermann 1922a), the latter two unlikely being seed dispersers. The forest weaver Ploceus bicolor Vieillot, 1819 was observed to feed on fruits of C. mackenii (Bleher et al. 2003). Stanford and Nkurunungi (2003) report differing preference of Coccinia plant parts by gorillas. Whereas the gorillas feed on the leaves and fruit pulp of C. mildbraedii but not the seeds, they take only the leaves of C. barteri.

Successful seed germination in Munich Botanical Garden indicates that passage through a digestive tract is not necessary at least for C. abyssinica, C. adoensis var. jeffreyana, C. grandiflora, C. grandis, C. hirtella, C. megarrhiza, C. microphylla, C. rehmannii, C. sessilifolia, and C. trilobata. However, whether seeds would survive intestine passage and the role of endozoochoric dispersal is also not known.

Many species of Coccinia bear extranuptial glands (nectar producing glands outside of the flower) on the lower lamina of the leaves and/or on the bracts and probracts (Figs 7b, 8a). The glands are sunken into the surface and are surrounded by cells with a thicker cell wall (Muhammad Ilyas 1992; pers. observ.). Ants take up the sweet-tasting sap in C. grandiflora (Zimmermann 1922b) and in C. grandis (pers. observ.). Whereas Ilyas (1992) reports aggressive behavior of the ants on herbivores for Indian C. grandis, the present author could not observe this in Tanzanian C. grandis. Nieuwenhuis von Üxküll-Güldenbandt (1907) found a weak attraction of ants and heavy damage by herbivores in C. grandis in Bogor Botanical Garden (Java, Indonesia). In addition, Zimmermann (1922b) does not find aggressive behavior in C. grandiflora either but reports that the ants attacked a caterpillar he had placed onto the plant. Agarwal and Rastogi (2008), on the other hand, report a significant reduction in residence time of herbivores on the cucurbit Luffa aegyptiaca when ants are patrolling on the plant. Most likely, there is no close relationship to certain ant species as guardians, and plant-defense is carried out only by a few ant species. How Coccinia species without or few probracts, bracts or sublaminal extrafloral nectaries (e.g., C. microphylla) react when damage by herbivores occurs, is unknown. Agarwal and Rastogi (2008) found an increase of total numbers of extrafloral nectaries over time but did not discuss changes of nectary density as reaction to grazing.

Some research has been undertaken on parasites and diseases for C. grandis for its status as crop but also as weed. As C. grandis is naturalized on several Pacific islands, in Australia, and the Neotropics, the plants can either overgrow other plants or represent a non-specific host for diseases of cucurbitaceous crops (Bamba et al. 2009; Muniappan et al. 2009). Its rapid growth can become problematic, as Pangelinan (2002) reports that C. grandis covered 35% of the vegetation of the island of Saipan only eleven years after its introduction.

Many different organisms are reported to live in, on, or to feed from Coccinia species. Beetle and fly larvae are either a disease for Coccinia, or in some cases, they are used to eradicate C. grandis. Fruits of C. grandis are a host for the larvae of the melon fly Bactrocera (= Dacus) cucurbitae (Coquillett, 1899), a tephritid fruit fly (Uchida et al. 1990). Bactrocera cucurbitae larvae usually populate the fruits but are also reported to hatch from galls (Murthy 1959). The galls are not produced by these flies, however, but by the gall midge Lasioptera (= Bimba) toombii (Grover, 1962) (Bhatia and Mahto 1968). The gall infestation is interpreted as non-specific, as the female fly might not be able to differentiate between the gall and an unripe fruit, which would be the usual target. In addition, also the tephritid fruit fly Dacus ciliatus Loew, 1862 infests the galls, sometimes even together with Bactrocera cucurbitae (Bhatia and Mahto 1968). The galls in C. grandis do not only result from Lasioptera toombii but can also be produced by the Itonidid gall midge Neolasioptera cephalandrae Mani, 1934 (Dharmamaraju 1968), which is reported to be the major disease in C. grandis in India (Unni et al. 1976). The galls induced by Neolasioptera cephalandrae also appear to be gateway for a fungal infection with a mold, which is identified tentatively as Cladosporium sp. (Krishnamurthy 1984).

Other major cucurbit pests can also use C. grandis as a host such as Diaphania (= Palpita) indica (Saunders, 1851) (Lepidoptera: Pyralidae), Aulacophora foveicollis (Lucas, 1849) (Coleoptera: Chrysomelidae), Leptoglossus australis (Fabricius, 1775) (Hemiptera: Coreidae), Aphis gossypii Glover, 1877 (Hemiptera: Aphididae), Liriomyza spp. leafminers (Diptera: Agromyzidae), Bemesia spp. white flies (Hemiptera: Aleyrodidae) (Bamba et al. 2009), and Epilachna vigintioctopunctata (Fabricius, 1775) (Coleoptera: Coccinellidae) (Maurice and Ramteke 2012).

As a result of the damage that can be done to cucurbitaceous crops and of its weedy behavior on Pacific islands, larvae of the clearwing moth (Sesiidae) Melittia oedipus Oberthür, 1878 and the weevil (Curculionidae) species Acythopeus burkhartorum O’Brian, 1998 and Acythopeus cocciniae O’Brian, 1998 were introduced to Hawaii for biological pest control against C. grandis (Muniappan et al. 2002). Immediately after hatching from the eggs, Melittia oedipus larvae bore into the stems, where they live and pupate after two to four months (Chun 2002). This moth, originating from Zanzibar (Oberthür 1878), appears to be quite specific as larvae only rarely develop on Cucumis sativus L. (Chun 2001). Also Zehneria guamensis (Merrill) Fosberg, a Guam endemic, is not attacked by M. oedipus (Bamba et al. 2009; Reddy et al. 2009). As C. grandis is a noxious weed in Hawaii (Hawaiian Department of Agriculture 1992) active search for pests for biological control was undertaken, which led to the discovery of two new beetle species from Kenya: Acythopeus burkhartorum whose larvae produce galls in young shoots, and A. cocciniae whose larvae mine the leaves (Chun 2002; O’Brian and Pakaluk 1998). O’Brian and Pakaluk report a close morphological similarity of both Acythopeus species to A. cucurbitae (Marshall), which is a major pest on various cucurbitaceous crops in Africa, the Middle East, and South India.

Many crop plants are attacked by root parasites or diseases, but there is little known from Coccinia. Only root lesion nematodes Pratylenchus dasi Fortuner, 1985 (nom. nov. for P. capitatus Das & Sultana, 1979) and P. crassi Das & Sultana, 1979 were described from the soil around the roots of C. grandis (Das and Sultana 1979; Siddiqi 2000), but it is not known if they harm the plants.

The only known plant parasite growing on Coccinia is the hemiparasitic vine Cuscuta chinensis Lam., which is reported to grow on C. grandis in Gujarat, India (Patel and Patel 2010).

Several fungi have been reported from Coccinia (Table 5). The rust fungus Puccinia windhoekensis Mennicken, Maier & Oberw. was described on Coccinia rehmannii (Mennicken et al. 2005), although Berndt (2007) noticed a great similarity of this rust to P. ctenolepidis Ramachar & Bagyanar. Berndt could not confirm the identity of the host specimen, so it seems to be likely that it was misidentified, since Ctenolepis cerasiformis looks quite similar to C. rehmannii.

There are several reports of plant viruses from Coccinia species. Purcifull and colleagues (1988) tested the infectability of several Cucurbitaceae to different plant viruses. They found that C. grandis can be infected by the papaya ringspot virus type W (PRSV-W) and the Trichosanthes virus but not by the cucumber mosaic virus, squash mosaic virus, watermelon mosaic virus-2, and the zucchini yellow mosaic virus. PRCV-W infections of C. grandis are also reported from several Pacific islands (Davis and Ruabete 2010).

Verma et al. (1983) suggest a yet undescribed mosaic virus, which is expressed in the occurrence of deformed leaves and a mosaic pattern in C. grandis leaves. A strain of the Moroccan watermelon mosaic virus, a Potyvirus, can infest Coccinia barteri (Owolabi et al. 2012), whereas the infection of C. sessilifolia with this virus, maybe a different strain, failed (van der Meer and Garnett 1987).

Several Coccinia species are used by tribal communities, mainly as a food source but also for cultural applications (for details see species descriptions). Coccinia grandis is notable for its economic value (although often cited erroneously as Coccinia cordifolia or C. indica), whereas the importance of C. abyssinica is only regional. Other species are used by local tribes only.

Coccinia grandis is used in a wide variety of applications. The plant is well-known in India, where its fruits had an impact even in classical Sanskrit literature. The red fruits are regularly used to describe lips, such as those of a beloved wife, who is described by her husband in Kālidāsa’s poem Meghadūta (Wilson 1867) or those of the goddess Sita and the god Rama in the epic Ramayana (Dutt 1891–1894). However, the fruits are also edible (raw when ripe and cooked when unripe) and are valued for their high content of carotenoids, esp. lycopene (Barua and Goswami 1979). Also young shoots and leaves are eaten as spinach and contain high amounts of lutein and other carotenoids (Addis et al. 2009; Wasantwisut and Viriyapanich 2003). The high carotenoid value is of special importance in developing countries, as vitamin A deficiency is widespread among young children and pregnant women (WHO 2009). Social marketing has proven to be valuable in promoting the use of C. grandis to prevent vitamin A deficiency (Chittchang et al. 1999). Domestication of C. grandis is in an early stage but promising cultivars are developed in South and SE Asia (Bharathi 2007; Engle et al. 1998; Ramachandran and Subramaniam 1983). Additionally, the leaves seem to be a good source of selenium and potassium, as well as vegetable protein (Xu et al. 2003; Xu et al. 2004). In Africa, C. grandis is mostly used from wild collections (Addis et al. 2009; Imbumi 2004). Contraindications to the use of C. grandis are also reported (Adanson 1757; Orech et al. 2005), but these might also be the result from either misidentification or regional chemo-varieties with differing amounts of secondary metabolites.

Coccinia grandis has been used in Indian traditional medicine for several hundred years (Nadkarni and Nadkarni 1976; Ramachandran and Subramaniam 1983). There are some studies that suggest a high potential for the use of C. grandis leaf extracts in diabetes treatment (Azad Khan et al. 1980; Kuriyan et al. 2008; Munasinghe et al. 2011). Parts of the observed effects are explained by inhibition of gluconeogenesis in the liver due to repression of glucose-6-phosphatase (Hossain et al. 1992) and fructose-1,6-bisphosphatase (Shibib et al. 1993). Also an activating effect on the promotor of the glucose transporter gene GLUT1 from rats is reported (Graidist and Purintrabipan 2009). Eshrat (2003) observes a positive effect of C. grandis in rats with hyperlipidemia, which is often connected to diabetes. However, its effectivity in diabetes treatment and the overall experimental design is in dispute (Ramachandran and Subramaniam 1983; Sadikot 2009), and more research to test the medical value is necessary. Since 2005, more than 15 studies researched chemical compounds in C. grandis and tested their validity in folk medicine. Some applications by tribal people could be reproduced ex situ but research is still in its infancy. Suggested effects are, e.g., anti-anthelmintic (Dewanjee et al. 2007b), anti-tussive (Pattanayak and Sunita 2009), hepatoprotective (Moideen et al. 2011; Vadivu et al. 2008), antioxidative (Umamaheswari and Chatterjee 2008), antipyretic, analgesic, and anti-inflammatory (Niazi et al. 2009), anti-ulcerogenic (Mazumder et al. 2008), and antimicrobial (Bulbul et al. 2011; Dewanjee et al. 2007a; Farrukh et al. 2008; Shaheen et al. 2009). Antimicrobial activity is explained by the occurrence of a protease inhibitor (Satheesh and Murugan 2011). Observed xanthine oxidase inhibition and antiuricaemical activity (Umamaheswari et al. 2007) suggests a use for gout treatment. Female rats with hyperprolactinemia-caused infertility regain fertility when treated with an aqueous extract of C. grandis stems and leaves (Jha et al. 2010).

Coccinia abyssinica is mainly an Ethiopian tuber crop. Under the name anchote, its starch containing (c. 20%) tubers are an important staple food in the SW semi-humid highland regions (Aga and Badada 1997; Asfaw 1997; Hora 1995). Additionally, the tubers contain a relatively high amount of calcium, which might explain the local belief that the plant helps with repairing bone fractures and displaced joints (Hora 1995). Locally (around Dembi Dolo, Oromia), young shoots and leaves are also eaten (Hora 1995). Although the fruits of the cultivated landraces are not eaten (Getahun 1973), the use might be beneficial due to the carotenoid content of the fruits, which are likely to be comparable to those of C. grandis. However, fruits of wild races of C. abyssinica are already used (Asfaw and Tadesse 2001). In Wollega (W Ethiopia), C. abyssinica is also used to treat gonorrhea, tuberculosis, and cancer, as well as in traditional ceremonies and celebrations and for animal fattening (Gelmesa 2010). Currently, much effort is put into the development of anchote to increase the yield by selection of cultivars with larger tubers and by improving crop growing with better suited fertilizers (Abera and Guteta 2007; Bekele et al. 2014; Mengesha et al. 2012).

Also other species of Coccinia are used as food sources but if so, then only locally. In these species, such as C. sessilifolia, some wild landraces lack bitter substances (Bosch 2004; Dinter 1912). Bitterness in Cucurbitaceae is mainly caused by triterpenoids called cucurbitacins, although not all cucurbitacins are bitter. Cucurbitacins are often cytotoxic and often exist as β-glucosides (Miró 1995). All Coccinia species screened so far contain cucurbitacins, although the cucurbitacin type, organ, and time of expression differ greatly. Whereas fruits of C. hirtella and C. quinqueloba contain glycosidic cucurbitacin B, C. adoensis from South Africa contains aglycosidic cucurbitacin B only in unripe fruits and traces of cucurbitacin D but not in ripe fruits (Rehm et al. 1957). Unripe fruits of C. rehmannii and C. sessilifolia are not bitter, and therefore lack bitter cucurbitacins (Enslin et al. 1956). Njoroge and Newton (1994) tested the type and distribution of cucurbitacins within the plant in different Cucurbitaceae and found in Kenyan C. adoensis plants cucurbitacins H, I, and R in the stem but no cucurbitacins in the roots, leaves, fruits, or seeds. Coccinia trilobata was found to contain the cucurbitacins B, D, and G in the stems, cucurbitacin D, H, I, and R in the leaves, and cucurbitacin G in the fruits, with no cucurbitacins in the roots and seeds. However, there seems to be much variability, as there are reports of edible (non-bitter) C. trilobata leaves (Coilly? 24, F. Msajiri 19). Coccinia grandis is also reported to contain cucurbitacin B (Bhakuni et al. 1962), and bitter and sweet fruited varieties are known. Guha and Sen (1973) find that cucurbitacin B has an antigibberelic effect, and its occurrence in seeds of C. grandis might enable or increase dormancy of the seeds.

Cucurbitaceae are also known for the occurrence of non-coded amino acids, such as citrulline in Citrullus lanatus (Thunb.) Matsum. & Nakai (Wada 1930). In a survey of such amino acids in CucurbitaceaeC. grandis and C. hirtella seeds were found to contain citrulline in low amounts, β-(pyrazol-1-yl)-L-alanine in very high amounts and the peptide Γ-L-glutamyl-β-(pyrazol-1-yl)-L-alanine in intermediate amounts (Dunnill and Fowden 1965). This pattern is similar to those that were found in Diplocyclos tenuis (Klotzsch) C.Jeffrey, Acanthosicyos horridus Welw. ex Hook.f., Peponium hirtellum Keraudren, Ruthalicia eglandulosa (Hook.f.) C.Jeffrey, Dactyliandra welwitschii Hook.f., and Ctenolepis cerasiformis (Stocks) C.B.Clarke (all in the same tribe as Coccinia).

Some Coccinia species are easily confused with collections of other Cucurbitaceae genera (Table 6). The similarity is sometimes striking and without generative structures, one might need some experience to differentiate between the genera.

There is no character that is useful for all species. For example, whereas the direction of the calyx lobes can be a useful character for some species (e.g., C. grandis, C. intermedia, C. keayana), it is less useful in others (e.g., in the C. quinqueloba clade). Collections without flowers are harder to identify. In some cases it is almost impossible to discriminate between species if flowers are lacking. Identification of only vegetative material is often possible but needs experience. The indumentum can be a useful character; especially the trichomes (length, somewhat also the shape) on the abaxial side of the petiole and the lower leaf lamina can be helpful. However, the trichomes on the adaxial side of the petiole and the leaf margin do not seem to have any purpose for species identification.

The key is made from observations of herbarium material but also includes some characters from personal observations of living material and observations as given on herbarium labels. Fresh material is not needed, however, to use the key. The term ‘articulate’ refers to dried trichomes that appear wrinkled due to equatorially sunken cell walls (see Fig. 3a) but not to trichomes with ramifications, which have never been observed in Coccinia. In the living state, these trichomes are rather long and stiff. The term “dentate” refers to the sometimes colored structures (hydathodes?) at the leaf margin and leaf tip (Figs 6, 7a, 8a, 16a, 16b, 21, 39).

Habitats in this key (not the species descriptions) are given rather crudely and reflect the vegetation that would be found naturally. Savannas and woodlands (tree stands with not largely overlapping canopies) can also include mopane, but also dry forests (larger amounts of deciduous trees and overlapping canopies), deciduous thickets, tall grasslands, and secondary vegetation derived from these. “Rainforests” include gallery forests, semi-deciduous forests derived from rainforests, e.g., in relict areas, perhumid savanna types, and open areas, in which rainforest would be predominant if it was not for human impact, or swamps.

A local key for Coccinia from West Africa is provided separately by Holstein and Renner (2011a). If the plant is collected from outside of Africa, then it is C. grandis.