Taxonomic significance of vegetative and reproductive morphology in southern Africa Rhynchosia sect. Rhynchosia (Fabaceae: Papilionoideae, Phaseoleae)

Rhynchosia is the largest genus in the subtribe Cajaninae, tribe Phaseoleae. Due to the lack of a recent taxonomic revision in the genus, the species are poorly known and as a result, are difficult to identify. As part of our ongoing taxonomic studies on the genus in southern Africa, this paper presents a comparative study of vegetative and floral morphological variation in the 47 species currently recognised in the type section Rhynchosia in the region. This is with a view to provide useful diagnostic morphological characters that can be used to correctly identify species in the type section and in other sections. The study used morphological data from field observation, herbarium specimens, and literature. Stems, leaves, and floral structures were examined with a dissecting microscope. A stereoscope with a camera lucida attachment was used to draw the reproductive morphology. Although morphological characters seem to overlap between the sections, characters such as leaflets size, type of indumentum on leaflet surfaces, stipules shape, type and length of inflorescences, presence or absence of indumentum on standard petals, presence and absence of sculpturing on wing petals, as well as length of upper lobes of the calyx are useful in identifying species.


INTRODUCTION
The significance of morphological characters in the taxonomy of the genera belonging to the family Fabaceae has been stressed by many researchers (Moteetee and Van Wyk 2006;Boatwright et al. 2010;Le Roux et al. 2010;Santos et al. 2012;Jeewon et al. 2013;Borges et al. 2018). Morphology has not only been useful in the identification and description of species within the family Fabaceae but has also been employed in phylogenetic studies and to understand the evolutionary patterns of plant taxa (LPWG 2017;Pinto et al. 2018;Silva et al. 2018). However, not all morphological characters are useful, while others are known to be more consistent, delimitative, or informative (Manoko 2007). For example, a superior ovary with one locule, two to many ovules arranged in two alternating rows on a single placenta, as well as marginal placentation are the most consistent characters that can be used to distinguish members of the family Fabaceae (Lewis et al. 2005).
The genus Rhynchosia Lour. belongs to the cosmopolitan family Fabaceae, tribe Phaseoleae, subtribe Cajaninae (Schrire 2005). It is the largest genus in its subtribe with a pantropical distribution and more than 230 species globally, ca. 55 in America, ca. 35 in Asia, ca. 69 in southern Africa, and ca. 64 in South Africa (Schrire 2005;Germishuizen 2006; Boatwright and Moteetee 2014;Ajao et al. 2018;Bezerra et al. 2019). Globally, it is found in America, Africa and Madagascar, Asia, and Australia. In Africa, its distribution ranges from West Africa (Ghana and Nigeria) to Tropical East Africa (Congo, Kenya, Tanzania, Uganda), Zambesiaca region (Botswana, Caprivi Strip, Malawi, Mozambique, Zambia, and Zimbabwe), and southern Africa (eSwatini, Lesotho, Namibia, and South Africa). In South Africa, it is found in all the nine provinces (Ajao et al. in preparation).
Previously, the South African species of the genus were revised by Baker (1923) whereby 59 species were recognized and placed in five sections, namely: Rhynchosia sect. Arcyphyllum (Elliott) Torr. & Gray., R. sect. Chrysoscias Benth., R. sect. Cyanospermum (Wight & Arnott) Benth., R. sect. Polytropia (Presl) Harv., and R. sect. Rhynchosia. However, Rhynchosia sect. Arcyphyllum is not represented in Africa as it is native to North America, hence the segregation of the R. densiflora (Roth) DC. group from the section to avoid phytogeographical confusion . Therefore, R. densiflora complex is currently recognized as a distinct group pending the outcome of the phylogeny of the genus Rhynchosia. Even though reproductive characters are regarded to be more important than vegetative characters, the latter can also be used to provide a distinction between species. Both characters have been used to delineate members of the family Fabaceae. For example, genera of subtribe Cajaninae, namely, Adenodolichos Harms, Bolusafra Kuntze, Cajanus DC., Dunbaria Wight & Arn., Eriosema (DC.) G.Don, Flemingia Roxb. ex W.T. Aiton, Paracalyx Ali, and Rhynchosia, are generally distinguishable from other members of the tribe by the presence of bulbous-based hairs, capitate trichomes, secretory-base trichomes and vesicular glands (Moteetee and Van Wyk, 2006;de Vargas et al. 2018;. Furthermore, within the subtribe, the genus Adenodolichos is identified by the presence of bracteoles (absent in all other genera), while the structure of the fruits is of diagnostic importance in separating the genera Cajanus and Dunbaria, where they are transversely grooved in Cajanus but not in Dunbaria. Expanded and papery calyx lobes after flowering is diagnostic of the species in the genus Paracalyx while the genus Flemingia is identified by the sub-digitate or rarely unifoliolate leaves. The genus Eriosema is distinguished from Rhynchosia by the following morphological characters: growth form or habit (subshrubs or erect, ascending, procumbent or prostrate, and never twining, vs. subshrubs or lianas/ erect, prostrate or twining), free or variably connate stipules (vs. always free stipules), absence of stipels (vs. stipels present in some species), hilum linear in shape (vs. hilum elliptical or oblong in shape), and funicle terminally attached to the hilum (vs. funicle centrally, subcentrally or occasionally terminally attached to the hilum) (Lackey 1981;Moteetee and Van Wyk, 2006;Cândido et al. 2019). A preliminary phylogenetic study in the genus by Manyelo (2014) revealed that the genus is not monophyletic as the other sections are embedded within the type section Rhynchosia.
In the ongoing taxonomic studies on the genus Rhynchosia in South Africa, reproductive and vegetative morphological characters have been successfully used to delineate species within groups, i.e. R. densiflora and R. totta groups and to revise Rhynchosia sect. Chrysoscias, R. sect. Cyanospermum, and R. sect. Polytropia (Moteetee et al. 2012;Moteetee et al. 2014;Moteetee and Le Roux 2016;. These morphological studies have also resulted in descriptions of a number of new species (Germishuizen 2011; Boatwright and Moteetee 2014; Ajao et al. 2018). The study here presented the morphological characters (reproductive and vegetative) of the species in the type section Rhynchosia in order to evaluate the characters that can be used to delineate species within the type section and between the other sections and group complexes.

MATERIALS AND METHODS
This study was based on the examination of herbarium specimens housed in BNRH, JRAU, and PRE (herbarium acronyms according to Thiers 2019) as well as on morphological observations of Rhynchosia species on the field. Stems, leaves, and floral structures were examined, and images were taken with a dissecting microscope with a digital camera attachment (OLYMPUS SZX2-TR30 JAPAN). Flowers were rehydrated in boiling water for 4-5 min, dissected under a binocular stereomicroscope and mounted in glycerol on a microscope slide for observation. A stereoscope with a camera lucida attachment was used to draw the reproductive morphology.
Data on both vegetative and reproductive morphology were taken from a minimum of five specimens per species in five replicates on each specimen except for some species with few available specimens. Also, a minimum of five mature flowers was dissected for each species with the exception of the species with few specimens available. Information regarding other sections and groups in the genus Rhynchosia was gathered from previously published studies from South Africa (Moteetee et al. 2012;Moteetee et al. 2014;Moteetee and Le Roux 2016;. The taxon (Rhynchosia sect. Rhynchosia) studied is predominantly distributed in South Africa with some of the species extended to other southern African countries such as Botswana, eSwatini, Lesotho, Namibia, and Zimbabwe. The terminology used in this study is in accordance with the morphological species concept, as adopted by Grear (1978) and Isely (1990).

RESULTS AND DISCUSSION
A comparison of morphological characters between the species studied is presented in Table 1. Author citations are included here and will not be repeated elsewhere.

Growth habit
Rhynchosia species in the type section Rhynchosia are perennial herbs or shrubs with trailing, climbing, prostrate or erect to sub-erect or woody to sub-woody stems. Out of a total of 47 species that are currently recognized in the type section, 18 have erect or sub-erect growth form, these include R. albissima, R. angulosa, R. bolusii, R. spectabilis, R. emarginata, R. pauciflora, R. sordia and R. sp. nov. (Ajao et al. in preparation). The remaining species such as R. caribaea, R. cilliata, R. fleckii, R. monophyla, and R. sublobata, have trailing, climbing, or prostrate stems (Table 1, Figure 1). However, stems are woody at the base in some climbing or trailing species such as R. capensis, R. coddii, R. fleckii, R. ovata as well as taxa in the R. totta complex group (R. totta var. totta, R. totta var. longicalyx, R. totta var. rigidula, R. totta var. venulosa (Germishuizen 2011;Moteetee and Le Roux 2016). In sections Cyanospermum, Chrysoscias and Polytropia, stems are climbing, twining and trailing, whereas in the R. densiflora group they are twining, erect or prostrate (Moteetee et al. 2012;Moteetee et al. 2014;).

Indumentum
Stems are usually glabrescent to pubescent pilose to tomentose, velvety or villous with bulbous-based hairs and vesicular glands. Species such as R. albissima, R. argentea, R. clivorum, R. crassifolia. R. emarginata, R. spectabilis, and R. waterberbergensis have tomentose stems, in R. woodi and R. angulosa it is cano-pubescent or cano-pilose, while in R. sordida it is silky silverypilose and pilose in R. ovata. Taxa in the R. totta complex have stems that are usually glabrescent or pubescent with short hairs which are brownish or grey when young (Moteetee and Le Roux 2016). However, the stems are glandular in species such as R. adenodes, R. arida, R. bullata, R. capensis, and R. cooperi ( Table 1). The indumentum type on the stems can be diagnostic as it can be used to distinguish between R. caribaea var. caribaea from R. caribaea var. picta in that it is pubescent in the former and tomentose in the latter.
Adaxial and abaxial surfaces of the leaves are usually glabrescent or pubescent to pilose or villous to velvety or tomentose, and glandular (yellow to orange or golden resin or dotted glands). Absence or presence of glands, and their distribution, can be of diagnostic importance in separating two morphologically similar species. For example, R. nitens shares tomentose stems and discolorous, silky silvery or velvety leaflets with R. galpinii. The former can be distinguished from the latter by the presence of glands on the surfaces, while they are absent in the latter. Rhynchosia adenodes can be easily confused with R. cooperi due to morphological similarities, i.e. having ovate-orbicular or subrhomboid leaflets, pubescent standard petals and axillary inflorescences with flowers arranged towards the apex. However, based on the distribution of glands, R. adenodes can be distinguished by its leaflets that are glandular on both surfaces while in R. cooperi they are glandular on abaxial surfaces only (Figure 2).

Leaf
Like most species in subtribe Cajaninae, the leaves of Rhynchosia sect. Rhynchosia are usually trifoliolate (Baker 1923), and rarely unifoliolate (e.g. R. waterbergensis) or having both types (R. monophylla, R. nervosa, and R. totta var. totta). In Rhynchosia sect. Cyanospermum and R. sect. Chrysoscias, the leaves are trifoliolate and never unifoliolate, whereas sect. Polytropia have trifoliolate to simply or pedately bipinnate, bi-tri-jugate, paucijugate, or supra-decompound leaves with R. densiflora group (R. densiflora subsp. chrysadenia var. chrysadenia (Taub.) Verdc. and R. densiflora subsp. chrysadenia var. Petiole and petiolule length is usually varied among the species, petioles are 1-63 mm long while petiolules are 2-30 mm long, and they are both usually pubescent to tomentose or pilose and glandular. Petiole length is of diagnostic importance in separating the different sections, for example, it is much longer in R. sect. Cyanospermum (up to 140 mm long), and much shorter in R. sect. Chrysoscias, (2.2-8.6 mm long), while R. sect. Polytropia and R. densiflora group range between the two Stipules are persistent, deciduous or caducous, pubescent or pilose to tomentose and glandular. They are quite varied in shape and can sometimes be useful in separating two morphologically similar species such as R. calvescens and R. caribaea which both have deltoid or rhomboid leaflets. However, the former can be identified by its deltoid stipules as opposed to lanceolate in the latter. Rhynchosia clivorum can also be identified by its large (7-13 × 4-6 mm), oblong-ovate stipules with aristate or caudate apex ( Figure 3C). Stipule shape can also be used to some extent to distinguish different sections, for example in R. sect. Cyanospermum stipules are elliptic-lanceolate while in R. sect. Polytropia, they are ovate, but in R. sect. Chrysoscias the shape is quite variable. Within the latter section, Rhynchosia leucoscias and R. angustifolia are morphologically related in that they both have broad oblong stipules while R. chrysoscias and R. microscias have ovate-lanceolate stipules (Moteetee et al. 2012. Stipels are usually absent in members of subtribe Cajaninae. How-  ever, there are few exceptions in some taxa of Rhynchosia sect. Rhynchosia (namely, R. adenodes, R. cooperi, and R. pentheri var. pentheri) where minute, caducous linear-lanceolate stipels occur. The presence of linearlanceolate stipels was also reported in R. sect. Cyanospermum (Moteetee et al. 2012).

Inflorescence
In Rhynchosia sect. Rhynchosia flowers are usually arranged in axillary or terminal racemes or umbels (Wood and Key 2009). However, sometimes inflorescences are in axillary racemes but arranged towards the apex or summit as in R. adenodes and R. cooperi ( Figure  4B). The inflorescence length ranges from 5 to 200 (280) mm, bears 1 to many flowers and can also be branched or unbranched. The inflorescence in R. sect. Cyanospermum, R. sect. Polytropia, and the R. densiflora group is an axillary raceme, while R. sect Chrysoscias has axillary umbels or solitary to sub-solitary flowers. On the other hand, the inflorescence is occasionally branched in R. sect. Cyanospermum (Moteetee et al. 2012;). The branching pattern as well as the length of the inflorescences can sometimes be of diagnostic importance within R. sect. Rhynchosia. For example, R. caribaea var. caribaea and R. caribaea var. picta can be separated from other species in southern Africa with deltoid, rhomboid, or ovate-rhomboid leaflets such as R. burchellii, R. atropurpurea, R. calvescens, R. sublobata, and R. thorncroftii, by their branched inflorescences.
The peduncle is usually glabrescent to pubescent or pilose to tomentose in the genus (Ajao et al. in preparation). Regarding the usefulness of inflorescence length in species delimitation, R. sordida is a species that is similar to R. angulosa in that the leaflets are elliptic. Rhynchosia sordida can be distinguished from the latter by the inflorescence that is usually shorter than the leaflets (5-15(30) mm) versus inflorescence that is longer than the leaflets (30-80(120) mm) in R. angulosa. Therefore, species in the type section of Rhynchosia can be grouped into two groups based on the length of inflorescences. Species such as R. cilliata, R. nitens, R. sordida, R. spectabilis, and R. komatiensis etc. have inflorescences that are shorter than the leaflets while species such as R. angulosa, R. atropurpurea, R. caribaea, R. clivorum, R. holosericea, and R. sublobata have inflorescences that are longer than the leaflets (Figure 4).
Flowers are usually pedicellate and yellow in all the species in the genus. To some extent, the number of flow-ers per inflorescence could be used to separate identical species in the genus. In the type section, for example, R. ovata is morphologically similar to R. reptabunda in that the stems are pilose, the leaflets are ovate or suborbicular and the bracts are persistent. However, R. ovata can be distinguished by its shorter inflorescence (35-60 mm long) with fewer flowers (2-4-flowered), whereas in R. reptabunda the inflorescence is 70-100(130) mm long and 4-9-flowered. Another example is found between R. bolusii and R. capensis which are similar in leaflet shape, but the former can be identified by its 1-or 2-flowered inflorescences vs. 1-6-flowered in the latter . In Rhynchosia sect. Polytropia, R. ferulaefolia is similar to R. pinnata in having a non-twining habit and clustered inflorescences, but they can be distinguished based on the number of flowers, i.e. 5-12 in the former and 5-8 in the latter .

Flower structure
The calyx is generally bilabiate in all the species in the genus, with unequal lips and lanceolate to acuminate, broadly lanceolate or obtuse lobes. The calyx tube is 1-6 mm long, the upper lobes are usually the shortest and are always connate almost to the apex, sometimes halfway and rarely below halfway, 0.3-13 mm long, the lateral lobes are 1.5-18 mm long while the carinal lobe is usually longer than the other lobes (2-21 mm long). The length of lobes, as well as the extent of connation of the upper calyx lobes, can be of diagnostic value within the type section and the R. densiflora group. A noteworthy example in the type section is found between R. sordida and R. angulosa which share elliptic leaflets as well as an erect habit. However, R. sordida can be distinguished by its much longer upper calyx lobes (6-10 mm) when compared to those of R. angulosa (1-3 mm) ( Figure 5). In the R. densiflora group, the upper lobes of the calyx are connate less than halfway to almost entirely, these character states are useful to separate the species in the complex. In R. densiflora subsp. chrysadenia var. chrysadenia, they are connate up to halfway while in R. densiflora subsp. chrysadenia var. connata they are connate more than halfway and sometimes to the apex (Jaca and Moteetee 2018). Rhynchosia sect. Cyanospermum and R. sect. Polytropia have upper calyx lobes connate to the apex while in R. sect. Chrysoscias, they are somewhat connate at the base.
Calyx indumentum varies from glabrescent to pubescent or pilose, villous to tomentose and glandular in the type section ( Figure 5), it is pubescent or pilose and glandular-punctate in the R. densiflora group, pubescent, glandular-dotted in R. sect. Polytropia and entirely velvety canescent or sometimes brownish pubescent at base in R. sect. Cyanospermum (Moteetee et al. 2012;Moteetee et al. 2014;).

Standard petals
Species in the type section have standard petals that are persistent, yellowish, purplish to brownish or brown-maroon veined, with or without callosities, 5-18 × 4-21 mm, claw (0.5) 1-3 mm. It also varies in shape from ovate to obovate or cordate to orbicular or elliptic in the type section, suborbicular in R. sect. Cyanospermum and R. sect. Polytropia, ovate to broadly obovate in R. sect. Chrysoscias and elliptic to oblong in R. densiflora group (Moteetee et al. 2012;Moteetee et al. 2014;. In terms of indumentum, the standard petals are glabrous and eglandular in all the sections and the R. densiflora group, with the exception of R. sect. Rhynchosia in which the standard petals are glabrous to pubescent or glandular. The indumentum on the standard petals is of great taxonomic importance as it can be used to separate morphologically similar species in this section. For example, R. sublobata and R. caribaea are similar in having deltoid or rhomboid leaflets, but the former can be differentiated by pubescent standard petals compared to glabrous in the latter. Also, R. caribaea var. picta can be differentiated from R. caribaea var. caribaea by its pubescent standard petals. Other species with pubescent and glandular standard petals in the type section are R.  adenodes, R, argentea, R. cooperi, R. crassifolia, R. galpinii, R. hirsuta, R. nitens, R. komatiensis, R. resinosa, R. spectabilis, R. vendae R. waterbergensis. In addition, Rhynchosia pentheri var. pentheri is occasionally glandular ( Figure 6). Despite the absence of indumentum on standard petals in R. sect. Chrysoscias, its size is of diagnostic value. The standard petal is larger in R. leucoscias (10.0-15.5 × 7.0-15.0 mm) when compared to R. microscias (8-11 × 6-9 mm) and R. leucoscias (9.5-13.0 × 7.5-12.5 mm) .

Wing petals
Oblong wings that are usually spurred at the base, 3-13 × 0.5-5.5 mm with linear claw 1-5 mm long is typical of the genus Rhynchosia. However, size, absence or presence of glands and surface sculpturing are of diagnostic importance. Wings are usually shorter than the keels in most of the species in the type section except in species such as R. clivorum R. cooperii, R. ovata, R. resinosa that have wings that are sometimes the same length as keel or even slightly longer than the keels as in R. argentea. Interestingly, in R. sect. Chrysoscias, the wing petals are equal to or longer than the keel petals in all species except in R. microscias, where they are slightly shorter than the keel. This character thereby separated R. microscias from the remaining species in the section . Furthermore, the wings are generally longer than keels in R. pinnata and R. smithiana in R. sect. Polytropia . Most of the species in the genus have glabrous wings with the exception of R. adenodes, R. albissima, R. atropurpurea, R. bullata, and sometimes R. pentheri var. pentheri (all in the type section), which have glandular wings. Surface sculpturing can either be present or absent in the species in the type section and can be used to separate identical species. For example, R. komatiensis and R. spectabilis with similar ovate-orbicular or ovate leaflets, are distinguishable by the presence of sculpturing on the wings of R. spectabilis. Furthermore, R. pauciflora and R. sp. nov. are similar in having erect habit, linear or oblong leaflets and 1-flowered inflorescence. However, the former is separated from the latter by the presence of sculpturing on wing petals (Figure 7). The presence of surface sculpturing on the wing petals is also of taxonomic value in R. sect. Polytropia as it is used to distinguished R. ferulaefolia (where it is absent) from R. pinnata and R. smithiana . However, it is absent in R. sect. Chrysoscias, R. sect. Cyanospermum, and the R. densiflora group.

Keel petals
Keel petals are uniform in shape in the genus Rhynchosia, they are usually yellow, veined, pocketed, rostrate or boat-shaped, 5-15 × 2-9 mm, with a claw, 1-5 mm long. They are usually larger than the wings with the exception of those mentioned in the previous section and smaller than the standard petals. However, in R. atropurpurea the keels are almost the same length as the standard petals and entirely purplish colour, hence the specific name atropurpurea (Figures 4C & 8). The colour of the keels in R. atropurpurea is the most important character to distinguish it from the remaining species in the genus.

Androecium
Stamens are uniform in the genus, and usually diadelphous with nine filaments fused and vexillary stamen free to the base. Anthers are also uniform, monomorphic, dorsifixed and somewhat dehiscent ( Figures  9A-B).

Gynoecium
Ovaries are elliptic-oblong to oblong-lanceolate, sessile to subsessile or stipitate, puberulous or pubescent to pilose or glandular in Rhynchosia sect. Rhynchosia. However, they are narrowly oblong and subsessile in other sections but vary in terms of indumentum as it is densely silky-villous and glandular-punctate in the R. densiflora group and pubescent in R. sect. Chrysoscias, R. sect. Cyanospermum, and R. sect. Polytropia (Moteetee et al. 2012; Moteetee et al. 2014;). Styles are usually glabrous but sometimes pubescent to pilose or glandular most especially at the lower part. In the type section, it is usually 4-18 mm long and the variation in length can be of diagnostic importance. For example, R. atropurpurea can be distinguished from R. calvescens by a longer style (13-15 mm) as opposed to the shorter style (7-10 mm) in R. calvescens (Figures 9C-D).

Fruits
The shape, size, and type of indumentum on the surface of the fruits vary greatly in the genus, but it can sometimes be of diagnostic importance. In the type section, fruits are 1-2-seeded, oblong to elliptic or falcate, 10-42 × 3-13 mm, compressed or inflated, stiped, glabrescent to pubescent or pilose to tomentose and glandular. It is important to note fruits of most species in this section are compressed and sometimes inflated as seen in R. sublobata ( Figure 10F). In R. sect. Cyanospermum, the fruits are narrowly oblong, 2-seeded, 15-20 × 5-6 mm, densely velvety canescent or rusty-brown pubescent. However, they are oblong, broadly-oblong to ovoid, and 1-2-seeded in R. sect. Chrysoscias while they are narrowly oblong, 2-ovuled, densely silky-villous, and glandular-punctate in the R. densiflora group (Moteetee et al. 2012;Moteetee et al. 2014;.

CONCLUSIONS
In this study, we investigated the reproductive and vegetative characters that can be used to delineate species within Rhynchosia sect. Rhynchosia and between the different sections in the genus Rhynchosia in southern Africa. The type section seems to more be variable, which might be due to the higher number of the species (47) as well as wider distribution in southern Africa when compared to the other sections. Within Rhynchosia sect. Rhynchosia, both vegetative and reproductive characters appear to be useful in the grouping of the species. These characters include growth habit, leaflet shape and indumentum as well as inflorescence length and type (branched or not), extent of connation of upper lobes of the calyx, indumentum on standard petals as well as presence or absence of surface sculpturing on the wing petals. However, structures such as stamen, pistil and keel petals are of lower taxonomic value as they tend to be similar within the section as well as between the sections. All the sections and the R. densiflora group overlap in terms of leaflet structure in that they all have either trifoliolate or unifoliolate leaflets with the exception of R. sect. Polytropia in which the leaves are trifoliolate to simply or pedately bipinnate, bi-tri-jugate, paucijugate, or supra-decompound. Rhynchosia sect. Chrysoscias and R. sect. Polytropia are morphologically related in that they both exclusively have lanceolate to linearlanceolate leaflets. It is worth mentioning that these two sections are restricted to the Eastern and Western Cape Provinces (South Africa).
Flowers can either be solitary, sub-solitary (e.g., R. sect. Chrysoscias) on in axillary inflorescences which are either racemes or umbels. Reproductive morphological characters are more variable in the type section when compared to other sections. Standard petals indumentum varies from being glabrous to pubescent or glandular in the type section, but they are consistently glabrous and eglandular in all other sections including R. densiflora group. Although, R. sect. Rhynchosia and R. sect. Polytropia appear to be related when it comes to the presence or absence of surface sculpturing on the keel petals which are consistently absent in R. sect. Arcyphylum, R. sect. Cyanospermum, and R. densiflora group. However, R. sect. Arcyphylum is close to R. sect. Cyanospermum in the twinning growth habit and the manyflowered inflorescences which occur in dense subsessile axillary raceme. Morphologically, there are a number of overlapping characters between the sections, but we are not oblivious of the fact that Baker's sectional classification is natural. Hence the reason phylogenetic relationships were also investigated between the sections in the genus in this study to determine whether Baker's sectional classification will be upheld when using a combination of morphological and DNA sequencing data.