Holotypus: Gabon. Ngounié: Parc National de Waka, 1°06′23″S 11°09′49″E, 5.X.2007, fl. & fr., Boussengui-Nongo & Bouango 245 (LBV!; iso-: BR!, MO).

Baissea atrobrunnea O. Lachenaud resembles B. subrufa Stapf in its densely felted twigs and coriaceous leaves, but differs by its lower leaf surface being densely and persistently felted with chocolate-brown indumentum (a character unique in the genus), its longer pedicels (3.5–7 mm vs. 1.5–3 mm) and its lanceolate corolla lobes, 4–5 mm long and more than twice as long as the tube (vs. ovate, 1.1–2.2 mm long and 0.7–1.4 times as long as the tube).

Lianas 4 m tall, covered on most of its organs (except corolla and upper side of mature leaves) by a short and dense felt of dark brown more or less dendritic hairs (Fig. 2). Branchlets cylindrical, 1.5 mm wide, brown-felted. Leaves opposite; blade elliptic, 10–13.8 × 2.3–3.5 cm, acute at base, acute or shortly acuminate at apex, thickly coriaceous, densely brown-felted on both sides when very young, upper side soon glabrescent and green, lower side with a persistent dark brown felt; midrib strongly impressed above, prominent below; secondary veins 4–6 pairs, widely spaced and strongly curved; tertiary veins hardly distinct; domatia absent; petiole 0.3–0.6 cm long, brown-felted. Inflorescences axillary and paired at nodes, laxly paniculate, 2–6.5 cm long, 10–25-flowered, brown-felted, branched from base; rachis 2–6.5 cm long, main branches 0.8–2.3 cm long; bracts minutely triangular, < 0.5 mm long, obtuse at apex. Flowers 5-merous; pedicel 3.5–7 mm long, brown-felted. Calices with 5 imbricate ovate lobes c. 0.7 × 0.6 mm, acute to obtuse at apex, brown-felted outside, glabrous inside, with c. 5 small colleters at base. Corollas yellowish-white; tube broadly infundibuliform, 1.5–2 × 1–2 mm, inside with 5 prominent ridges alternating with lobes, glabrous outside, inside with a ring of deflexed hairs above stamens; lobes lanceolate, 4–5 × 0.7–1 mm, obtuse at apex, glabrous; flower bud cylindrical, obtuse at apex. Stamens fully included, inserted 0.3 mm above base of corolla tube, subsessile; anthers 2 × 0.4 mm, acute at apex, glabrous except puberulous connective. Pistils included; ovaries truncated cone-like, 0.5 mm long, densely villose at apex, 2-carpellate; styles 1.2 mm long, glabrous, with narrowly cylindrical base 0.2 mm long, fusiform median part 0.3 mm long and subulate stigma 0.7 mm long. Fruits consisting of 2 narrow, almost cylindrical follicles 16.5–18.5 × 0.6–0.8 cm, densely brown-felted, forming a very obtuse angle with each other; pedicel woody and thickened. Seeds not seen.

Distribution, ecology and phenology. – Only known from the type collection in central Gabon (Waka National Park); habitat not recorded but presumably evergreen forests. It is not known whether the species is truly rare, since its area of origin is little-prospected; however, it is presumably very local, having not been found elsewhere in Gabon during recent inventories (despite being readily recognisable on the field). Flowers and fruits were collected in October, corresponding to the onset of the first rainy season.

Conservation status. – Baissea atrobrunnea is endemic to Gabon and known from a single collection; its Extent of Occurrence (EOO) therefore cannot be calculated. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 4 km^2, within the limit for “Critically Endangered” status under Criterion B2. Its only known occurrence is located within the Waka National Park, very close to the boundary of the park. With no precise data about its ecology, and considering that its area of origin is poorly explored, it is unclear whether the species is threatened or not, and it seems reasonable to include it in the “Data Deficient” [DD] category.

Notes. – This species is readily recognisable, even in the vegetative state, by its strongly discolorous leaves with a dark chocolate-brown underside; hence the specific name. Its closest relative is probably Baissea subrufa (see diagnosis for the similarities and differences). The peculiar indumentum of B. atrobrunnea and B. subrufa, which consists of inflated ramose hairs (Fig. 2) is also found in the morphologically related genus Motandra, and it is a question whether the two genera are really worth keeping separate. They differ chiefly in the shape of their anther-tails, which are straight and acute in Baissea, curved and obtuse in Motandra. Oncinotis, also closely related, has anthers similar to Motandra but differs from both genera by the presence of coronal appendages between the corolla lobes at the rim of the tube.

≡ Oncinotis campanulata K. Schum. in Bot. Jahrb. Syst. 23: 227. 1896.

Lectotypus (designated by Van Dilst, 1995: 102): Cameroon. Central Region: Yaoundé, s.d., Zenker & Staudt 19 (BM [BM000925817]!; isolecto-: NY).

= Baissea laurentii De Wild., Not. Pl. Ut. Congo 2: 253. 1908. Holotypus: D.R. Congo. Province Orientale: Romée, I.1906, fl., M. Laurent 1362 (BR [BR0000008824615]!; iso-: BR [BR0000008825032, BR0000008824622]!, YBI [YBI169747992] image!).

= Baissea goossensii De Wild., Pl. Bequaert. 5: 417. 1932. Holotypus: D.R. Congo. Province Orientale: Barumbu, V.1921, fl., Goossens 1670 (BR [BR0000008824929]!; iso-: BR [BR0000008824653]!, MO-2415948 image!).

Distribution and ecology. – Widespread from Côte d'Ivoire to central D.R. Congo; occurs in forest edges, usually along rivers, up to elevations of 1200 m.

Notes. – Baissea campanulata is here considered in its narrow sense, excluding B. congensis and B. subsessilis that were both placed under synonymy by van Dilst (1995). Differences between the three taxa are summarised in Table 1. Baissea campanulata is the most widespread of the three; its range locally overlaps with B. subsessilis in western Cameroon. No material has been seen from Nigeria; specimens from this country cited in the revision by van Dilst (1995) correspond to B. subsessilis.

The inflorescences in Baissea campanulata can be terminal or axillary, often in the same branch; terminal inflorescences are always lax, while axillary ones are usually congested (but can be laxer, e.g. in Le Testu 8852, L. Dubois 136 or J. Léonard 1172). Some specimens (Breteler et al. 8944, M. Laurent 1362, J. Léonard 1172, Mandango 2879) also show a remarkable dimorphism in size and shape of corolla lobes: the flowers from terminal inflorescences (and sometimes from the upper leaf axils) have remarkably long and narrow, almost linear corolla lobes up to 18 mm long, while those borne lower down on the twigs have the corolla lobes much shorter and triangular, not exceeding 5 mm long.

Lectotypus (first-step designated by van Dilst, 1995: 110; second-step designated here): Liberia. Grand Bassa: Grand Bassa (= Buchanan), 9.IV.1896, fl., Dinklage 1630 (K [K000233867]!; isolecto-: A [A00078659] image!, K [K000233868, K000233869]!, Z [Z-000000982] image!).

Distribution and ecology. – Restricted to Liberia and southwestern Côte d'Ivoire (Fig. 3), where it occurs in wet evergreen forests near the coast.

Notes. – Both Huber (1963) and van Dilst (1995) treated this species as a synonym of Baissea lane-poolei, but the two taxa differ in inflorescence characters and also in ecology. Baissea concinna has a lax inflorescence and most flower pedicels are > 4 mm long; it grows in wet evergreen forests near the coast. Baissea lane-poolei has a congested inflorescence and flower pedicels up to 4 mm long; it grows in semideciduous forests or gallery forests, usually in hilly inland areas (Fig. 3).

The first author did see both species in the field in their current known distribution. Nevertheless, both species were never observed in the other forest areas of Liberia despite several visits.

Van Dilst (1995: 110) cited the holotype at K. Three specimens are desposited in K and the specimen K000233867 annotated “holotype” by van Dilst in 1993 is here formally designated as the lectotype.

Additional specimens examined. – Liberia. Sino: Greenville, 18.III.1948, fl., Baldwin 11560 (K).

Côte d'Ivoire. Tabou: 13 km NW of Tabou, 12.IV.1974, fl., Breteler 7386 (WAG); close to Pata-Idié, 11.IV.2000, fl. bud, Jongkind & Assi-Yapo 5081 (WAG).

≡ Zygodia congensis R.D. Good in J. Bot. 67 (Suppl. 2): 89. 1929.

Holotypus: Angola. Cabinda: Lufo River, near Belize, 29.III.1919, fl., Gossweiler 7959 (K [K000233966]!; iso-: BM [BM000925816]!, COI [COI00070733] image!, MO-1302577 image!).

Distribution and ecology. – Restricted to Gabon (Ngounié and Nyanga provinces) and Angola (Cabinda), and probably Republic of Congo (where not collected yet); occurs in forest edges, often along rivers, at elevations of 10–640 m.

Notes. – This species, previously treated as a synonym of Baissea campanulata (see comments under the latter species) is resurrected here. Since it was originally described in Zygodia Benth., a genus synonymised with Baissea by Pichon (1948), the new combination is required.

Additional specimens examined. – Gabon. Ngounié: 40 km E. of Mouila, along the road to Yeno, 28.XI.1984, fl., Arends et al. 501 (WAG, LBV); Sindara, 27.IX.1917, fl., Le Testu 2227 (BM, BR, P); ibid. loco, 22.III.1926, fl., Le Testu 5867 (BM, BR, P); Mbigou, 3.V.1925, fl., Le Testu 5415 (BM, BR, P); ibid. loco, 17.IV.1930, fl., Le Testu 8032 (BM, BR, P); Epambwa, 18.III.1927, fl., Le Testu 6427 (BM, BR, P); 50 km along Mouila-Yeno road, 31.III.1988, fl., de Wilde & Jongkind 9639 (BR, LBV, WAG). Nyanga: sur la route entre Mabanda et Ndendé, 9.IV.2018, fl., Bidault et al. 4363 (BR, G, MO, WAG); along Nyanga river, upstream from Mayonami, 16.III.1994, fl., Wieringa et al. 2495 (BR, G, K, LBV, P, WAG).

Holotypus: Sierra Leone. Western Area: York Pass, 7.VII.1914, fl., Lane-Poole 322 (K [K000233866]!; iso-: GB).

Distribution and ecology. – A West African endemic, widespread in the hill ranges of Guinea, Sierra Leone (north and Freetown Peninsula), northern Liberia (Nimba area) and western Côte d'Ivoire (around Man) (Fig. 3); occurring in semideciduous or gallery forests up to elevations of 1400 m.

Notes. – This species is here considered in its narrow sense, excluding Baissea concinna, which is treated as a distinct species (see comments under it).

≡ Oncinotis subsessilis K. Schum., Bot. Jahrb. Syst. 33: 321. 1903.

Lectotypus (designated by van Dilst, 1995: 102): Nigeria. Lagos State: Ishagama (Jorubaland), III.1899, fl., Schlechter 12310 (K [K000234015]!; isolecto-: AMD [AMD.25157] image!, BM [BM000925815]!, BR [BR0000008825087]!, G [G00009017, G00009018] images!, L [L0004439, L0004438] images!, P [P00413270, P00413271] images!, WAG [WAG0003984]!, Z).

Distribution and ecology. – Restricted to southern Nigeria and adjacent south-western Cameroon, occurring in lowland rainforest edges up to elevations of 250 m.

Notes. – This species, like Baissea congensis, was included in the synonymy of B. campanulata by van Dilst (1995); see additional comments under the latter species. It can be separated from both B. congensis and B. campanulata by its much hairier stems and leaves (see Table 1). Its distribution locally overlaps with that of B. campanulata in Cameroon, but is widely separated from that of B. congensis.

Additional specimens examined. – Nigeria. Cross River State: Eko-Esai, 18.III.1977, fl., Ariwaodo 699 FHI 88762 (WAG); Iyamoyong Forest Reserve, 12.V.1959, fl., Binuyo FHI 41294 (BR, WAG). Ogun State: Ijebu Igbo, 24.IV.1949, fl., Ejiofor FHI 26114 (BR, K). Oyo State: Gambari, 9.V.1966, fl., van Eijnatten 1475 (WAG); Gambari, 15.V.1974, fl., Gbile FHI 73085 (P).

Cameroon. South-West Region: S of Baro Village, 31.III.1988, fl., D.W. Thomas et al. 7468 (MO, WAG).

Hunteria

The genus Hunteria was revised by Omino (1996), along with the closely related genera Picralima Pierre and Pleiocarpa Benth. These genera, together with Gonioma E. Mey., form the tribe Hunterieae (Endress et al., 2018). The members of this tribe are trees or shrubs displaying left-contorted corolla aestivation, absence of corona, anthers included and fertile to the base, absence of disk, and fleshy fruits with separate carpels. The great similarity between Hunteria, Picralima and Pleiocarpa suggests the need of merging them, though in the absence of phylogenetic data we have followed the traditional classification. Hunteria differs from Picralima by its smaller fruits with fleshy (not hard) pericarp, its seeds with membranaceous (not coriaceous) testa and cotyledons lacking secondary veins, and its sepals imbricate only in bud stage (vs. imbricate even at anthesis) (Omino, 1996). Differences with Pleiocarpa are discussed under the latter.

A new species of Hunteria is described here based on recent collections from Gabon. The genus now includes 13 species, all of which are African except for H. zeylanica (Retz.) Gard. ex Thw. that reaches Asia (Omino, 1996; Endress et al., 2018).

Holotypus: Gabon. Estuaire: entre Kinguélé et Tchimbélé, au sud de Makaban, le long de la Bangoui, 0°31′N 10°17′E, 320 m, fl., 28.X.2020, Bidault et al. 5144 (MO!; iso: BR!, BRLU!, G!, LBV!, MA!, P!, WAG!).

Hunteria maasiorum Jongkind & E. Bidault resembles H. simii (Stapf) H. Huber in its laxly umbellate inflorescences, oblong monocarps ending in a long beak, and leaves with well-spaced and curved lateral veins, but differs by its conspicuously longer calyx lobes (4.5–6 mm vs. 1–1.3 mm), longer corolla lobes (12–16 mm vs. 7–12 mm) and larger seeds (17–24 × 11–13 × 5–8 mm vs. 11–15 × 6.5–8.5 × 5.5–6.5 mm).

Shrubs or treelets, up to 5 m tall. Leaves glabrous; blade elliptic, 17.5–25 × 6.8–10 cm, acute at base, acuminate at apex, slightly coriaceous; midrib narrowly channelled above; secondary veins 8–10 pairs, often with 1–3 less conspicuous secondary veins in between, ascending and slightly curved, forming a submarginal vein and an angle of 45–60° with midrib; tertiary venation inconspicuous; petiole 10–15 mm long. Inflorescences terminal, sometimes axillary, glabrous except for corolla, umbellate, 3–10-flowered, with a peduncle 3–5 mm long. Flowers 5-merous, with pedicels 4–10 mm long. Calyx lobes 4.5–6 × 1–2 mm, gradually narrowing from base to apex, glabrous, with a row of small colleters inside at base, slightly spreading. Corollas white, in bud up to 28–30 mm long, glabrous outside; tube in open flower 16–21 × 2–4 mm, almost cylindrical with a slight widening at level of stamens, inside with sparse hairs around pistil head; lobes overlapping to the left, 12–16 × 3–7 mm, spreading, rounded at apex, entirely glabrous. Stamens included, inserted towards upper third of corolla tube; anthers 1.7–2.1 × 0.8–1 mm, subsessile, glabrous. Pistils c. 7 mm long, glabrous, not reaching base of stamens; ovary ovoid, c. 2 × 1 mm, style c. 3.7 mm long, pistil head ovoid with stigmoid apex, c. 1.3 × 0.7 mm. Fruits yellowish, smooth, glabrous, of two separate mericarps divergent at an angle of 180°, mericarp c. 7 × 2 cm, bluntly acuminate at apex. Seeds smooth, variable in shape but all flattened and more or less angular, 17–24 × 11–13 × 5–8 mm; embryo c. 1 cm long.

Etymology. – Hunteria maasiorum is named after Paul Maas and Hiltje Maas-van de Kamer, who discovered the species during an expedition to Gabon in 2011.

Distribution, ecology and phenology. – This species is endemic to the south-west of the Cristal Mountains in northern Gabon (Fig. 6), where it occurs in the understory of wet evergreen forests, both mature and degraded, at elevations of 35–330 m. It appears to favour rocky areas with an open understory, often along rivers, but has also been collected on drained soils. Flowers have been collected in October and November, and fruits in November, corresponding to the main rainy season.

Conservation status. – Hunteria maasiorum is known from seven collections made between 2011 and 2021, all from the Monts de Cristal area, in Gabon. All the occurrences are considered extant considering the still important forest cover in those areas, and the recent dates of collection. Based on a 2 × 2 km cell size, the AOO of this species is estimated as 28 km^2, below the upper threshold for “Endangered” status under Criterion B2. The EOO is calculated as 62 km^2, below the upper threshold for “Critically Endangered” status under Criterion B1. Two collection sites are located within the Monts de Cristal National Park, sector Mbé. Two other occurrences are located within a logging concession, and are threatened by activities linked with logging, inducing a decline in its habitat quality. Two collection sites, situated outside the National Park at its southern tip, are within the construction site of a planned hydro-electric project, and therefore threatened by it. We expect this location will disappear in the future. One collection site situated within the NP is nonetheless within the projected inundated area resulting from the dam project. It is therefore also threatened by it, and expected to disappear in the future. The other site located within the Monts de Cristal NP does not show any evidence of threat. The last site is situated outside the NP, between a road and a power line, and is threatened by the maintenance of those infrastructures that involves a degradation of its habitat quality. As a consequence, these six occurrences represent four locations (sensu IUCN 2019), with regard to the most serious plausible threat (hydro-electric projects), under the upper limit for “Endangered” status. We infer a past, current, and future continuous decline in the extent and quality of habitat consequently to all the threats above mentioned. We also infer a future decline in the EOO, AOO, number of locations and number of mature individuals of this species, due to the hydro-electric project. This species is thus assigned a status of “Endangered” [EN B1a b(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)].

Notes. – This is a very distinctive species when fertile, with its large calyx and corolla (the largest recorded in the genus) and narrow beaked mericarps. Its closest relative is presumably Hunteria simii, which in addition to the differences mentioned in the diagnosis has a widely separate distribution, being found from Sierra Leone to Côte d'Ivoire. Other species of Hunteria have a much smaller corolla (tube ≤ 13 mm long, lobes ≤ 8.8 mm long) and calyx lobes (≤ 2.5 mm long), and mericarps globose to broadly ovoid (although fruits of H. densiflora Pichon and H. myriantha Omino are not yet known). In addition, most of them have the secondary leaf veins more numerous and almost straight, forming a broader angle with the midrib; except for H. myriantha and H. hexaloba (Pichon) Omino which are similar to H. maasiorum in this respect.

In the flowering stage, Hunteria maasiorum could be mistaken for Petchia africana Leeuwenb., which has a very similar inflorescence, calyx and corolla, except that the latter is bright yellow. The leaves of P. africana are more abruptly cuspidate at the apex and have more numerous secondary leaf veins (12–20 pairs) forming an almost straight angle with the midrib.The long moniliform mericarps of Petchia are very different from those of Hunteria.

In vegetative characters, Hunteria maasiorum is very similar to H. hexaloba and Pleiocarpa robusta (described below), but these two species have the leaf midrib not channelled above but somewhat prominent. They also differ in their subsessile flowers, much smaller calyx, and shortly ovoid mericarps.

Additional specimens examined. – Gabon. Estuaire: Monts de Cristal, Kinguélé, vallon à l'Ouest de la Mbé, 0°24′03″N 10°15′18″E, 19.IV.2021, fl., Bidault et al. 5326 (LBV, MO); Monts de Cristal, site du chantier du barrage hydroélectrique de Kinguélé Aval, 0°23′N 10°14′E, 19.XI.2020, st., Klein et al. 38 (BRLU, LBV); Monts de Cristal, à l'est de la route Kinguélé-Andok Foula, 106 m, 0°24′N 10°14′E, 24.X.2020, fl. buds [very young], Lachenaud et al. 3139 (BRLU, LBV, MO); Parc National de Monts de Cristal, road L108 from Kinguélé to Tchimbélé, 0°29′N 10°17′E, 327 m, 24.X.2011, fl. bud, Maas et al. 9964 (LBV, WAG); side road at km 46 of road from Kougouleu to Méla, 0°33′N 10°15′E, 21.XI.2011, fr., Maas et al. 10415 (LBV; WAG); Monts de Cristal, bords de la route de Kinguélé Aval, 0°25′N 10°15′E, 34 m, 26.XI.2020, st., MBG Transect 6360 (BRLU).

Landolphia

Landolphia is a genus with 60 species, including the new species published here, and is endemic to Africa and Madagascar (van Dilst, 1999; Endress et al., 2018). It belongs to tribe Willughbeieae, subtribe Landolphiinae, a group of climbing (or rarely suffrutescent) plants with left-contorted corolla aestivation, absence of corona, anthers included and fertile to the base, syncarpous ovaries, and fleshy fruits with albuminate seeds. Landolphia is by far the largest genus in this group; most other genera of the subtribe appear to be little more than satellites of Landolphia, and their position in relation to the latter needs further investigation, which is outside the scope of this paper.

The last revision of Landolphia for continental Africa was published almost 30 years ago (Persoon et al., 1992) and many new specimens have been collected since. A review of the material from Atlantic Central Africa resulted in the discovery of four new species, which are described here. Two of them are based on recent collections not seen by the authors of the last revision; the other two, L. verrucosa Jongkind & O. Lachenaud and L. obovata O. Lachenaud & Jongkind, had previously been mistaken for L. owariensis P. Beauv. and L. glandulosa (Pellegr.) Pichon, respectively. The latter species, treated here in its strict sense, is a rare Gabonese endemic, and a new description of it is presented since that in Persoon et al. (1992) is largely based on material here referred to L. obovata. Landolphia owariensis remains a very widespread and common species, for which Persoon et al. (1992) presented an accurate description.

Holotypus: Gabon. Woleu-Ntem: 0.5 km E of Tchimbélé, 27.IV.1990, fl., Wieringa 778 (WAG [WAG.1610518]!; iso-: BR [BR0000014318498]!, E, K, LBV [LBV0000844]!, MO).

Landolphia anthonii Jongkind resembles L. incerta (K. Schum.) J.G.M. Pers. with its axillary inflorescences, very short corolla tube (1.7–2 mm), long and narrow corolla lobes, and glabrous stems and leaves; but it has a more compact inflorescence, the anthers are not long acuminate but rounded at apex, the leaves are gland-dotted and with more prominent lateral veins below and the midrib of the leaf is channelled above, not prominent (when dried). In these characters it resembles L. ferrea J.G.M. Pers., L. glabra (Pierre ex Stapf) Pichon and L. persooniana O. Lachenaud & Jongkind, but these species have a much longer corolla tube (6–13 mm).

Lianas large with tendrils and white latex. Branches smooth except for scattered and inconspicuous lenticels; branchlets 1–2 mm thick, glabrous, smooth. Leaves opposite, glabrous; blade narrowly elliptic or ovate, 6.5–9.5 × 2–3 cm, coriaceous, cuneate or rounded at base, caudate at apex, glandular dots conspicuous on lower leaf surface (1–4 per cm^2), blackish when dried; midrib channelled above, prominent below; 12–17 pairs of secondary veins, forming an almost straight angle with midrib, alternating with (slightly) fainter parallel veins and connected by a slightly looping submarginal vein; tertiary venation laxly reticulate, invisible above and not very conspicuous below; petiole 4–6 mm long. Inflorescences axillary, cymose and highly contracted, up to 1.5 cm long (flowers included), 5–7-flowered, glabrous; peduncle up to 3 mm long; bracts triangular to ovate, < 1 mm long, ciliate. Flowers 5-merous; pedicel 1–1.5 mm long, glabrous. Calyx lobes imbricate, triangular to ovate, c. 1 × 1 mm, acute to obtuse at apex, ciliate, green. Corollas white, yellow in bud; tube 1.7–2 mm long, ± cylindrical, glabrous on both sides; lobes 9–12 × 1.5–2 mm, hairy at base inside. Stamens subsessile, about half as long as corolla tube and inserted around mid-height, anthers almost 1 mm long, glabrous. Pistils 1.3–2 mm long, glabrous, ovary c. 1 mm long, ovoid with several longitudinal ridges, style absent or very short, pistil head c. 0.3 mm long with annular base and short stigmoid apex. Fruits unknown.

Etymology. – This species is named after Anthonius J.M. Leeuwenberg (1930–2010), who first identified its type as a probable new species in 1992. Leeuwenberg was the leading expert on African Apocynaceae in his time, and contributed many generic revisions that have greatly advanced our knowledge of the family.

Distribution, ecology and phenology. – Occurs in the hill ranges of southern Cameroon (Akom II area) and Gabon (Cristal Mountains, Chaillu Massif) (Fig. 8A), in wet evergreen forests, at elevations of 500–1000 m. Flowers have been collected in March, April and July.

Conservation status. – Landolphia anthonii occurs in mid-altitude forests (500–1000 m) in Cameroon and Gabon, and is known from four collections representing four distinct localities. Considering the still important forest cover in the areas where it was collected, we consider that these sites are still extant. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 16 km^2, which falls within the limits for the “Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) is calculated as 15,687 km^2, which falls within the limit for “Vulnerable” status under Criterion B1. The only occurrence in Cameroon is in a protected area, Campo-Ma'an National Park. The three occurrences in Gabon are not protected (although one is very close to the limits of Monts de Cristal National Park, where the species may well occur) and have all been exposed to past and present forest exploitation; whether this represents a threat to the species is unclear, since little is known of its ecological requirements, and many liana species (including other Landolphia) may actually benefit from moderate levels of forest disturbance. Also, as a tall liana with small flowers, the species is likely to be undercollected. With the two most remote localities more than 500 km apart this is even more likely. According to the limited data available at this moment, and using the IUCN criteria, we cannot reach a realistic threat category, and therefore L. anthonii is included in the “Data Deficient” [DD] category.

Notes. – The corolla tube of this species is among the shortest recorded in the genus, resembling that of Landolphia incerta (see the diagnosis for differences). However, in vegetative characters L. anthonii is closer to L. ferrea, L. glabra and L. persooniana; all four species share small (usually < 10 cm long), glabrous leaves with the midrib channelled above and the lateral veins inserted almost at a right angle, and also highly contracted inflorescences and very slender corolla lobes (their differences are summarised in Table 2). The distinction between L. anthonii and L. glabra is difficult in absence of flowers, although twigs of the latter are usually more strongly lenticellate. It is not known if there are additional differences in the fruits, since those of L. anthonii are not known; the label of Tchouto et al. 2853 mentions green fruits, but none are present on the WAG sheets.

Additional specimens examined. – Cameroon. South Region: Campo-Ma'an area, Efoulan, Ongongo and Nkolomekok hills in Akom II area, 2°44′43″N 10°31′48″E, 1000 m, fl., 25.IV.2000, Tchouto Mbatchou et al. 2853 (WAG).

Gabon. Ngounié: Bordamur logging concession, 0°41′S 11°13′E, 600 m, 1.III.2009, fl., Stévart et al. 3150 (BR, MO); Mts. Du Chaillu, 5 km SE of confluence of Ogoulou and Ogoudou Rivers, 1°53′S 11°28′E, 660 m, 8.VII.1989, fl. bud, Wilks 1978 (MO, WAG).

≡ Carpodinus glandulosa Pellegr. in Bull. Mus. Nat. Hist. Nat. 31: 465. 1925.

Holotypus: Gabon. Nyanga: Tchibanga, 7.I.1915, fl., Le Testu 1968 (P [P00105629]!; iso-: BM [BM000925662, BM000925663] images!, BR [BR0000008858825]!, E [E00193155] image!, K [K000233288] image!, LISC [LISC002907] image!, P [P00105630, P00105631]!).

Lianas large. Branchlets 2–3 mm thick, dark brown with conspicuous paler lenticels, glabrous or sparsely puberulous at nodes. Leaves opposite; blade obovate, 4.8–12 × 2.2–5.2 cm, acute at base, rounded or acuminate for up to 1 cm at apex, glabrous, rather shiny, drying olive green to olive brown, glandular dots conspicuous on lower leaf surface (1–4 per cm^2), blackish to reddish when dried; midrib impressed above, raised below; 6–10 pairs of curved and conspicuously looping secondary veins; tertiary venation laxly reticulate; petiole 3–5 mm, glabrous, with numerous colleters in its axil. Inflorescences 1–2-flowered, axillary, fasciculate. Flowers 5-merous; pedicel ≤ 1 mm long, tomentose; bracteoles 2, opposite, at base of calyx, narrowly elliptic to narrowly obovate, 2.5–3 × 1–1.3 mm, obtuse to acute at apex, concave, puberulous outside, glabrous inside. Calyx lobes imbricate, suborbicular to broadly ovate, about as long as wide, 3.3–4 × 3.3–4 mm, slightly unequal (outer lobes smaller), rounded to emarginate at apex, thickened at base, glabrous except ciliate margin, inside with several basal colleters. Corollas creamy white; tube c. 14 × 1 mm (at base), 2.3 mm around anthers and 2 mm at throat, cylindrical at base, then broadening in upper third and slightly constricted at throat, glabrous outside, sparsely pubescent inside in upper third; lobes overlapping to left, lanceolate, c. 9 × 2.3 mm, ciliate on right margin, otherwise glabrous. Stamens 2.5 mm long, inserted around upper 1/4 of tube, included; filaments 0.5 mm long; anthers c. 2 × 0.5 mm, acute at apex, glabrous, their tips reaching c. 0.5 mm below throat. Pistils c. 12.3 mm long; ovary 1.5 × 1 mm, obovoid, densely pilose; style cylindrical, 9 mm long, glabrous; pistil head ± cylindrical, 0.8 × 0.8 mm; stigmoid apex cylindrical, 1 × 0.5 mm. Fruits dull white with faint greenish tinge, obovoid, rounded at apex, 6.5 × 4.5 cm, glabrous, strongly wrinkled in dry state, pulp yellow. Seeds irregularly ellipsoid and compressed.

Distribution, ecology and phenology. – Endemic to Gabon, only known from two localities in Estuaire (Remboué River) and Nyanga (Tchibanga) provinces (Fig. 8B); presumably in lowland evergreen forests, but no precise ecological information is available from the collectors. Flowers and fruits have both been collected in January.

Notes. – This species is here considered in its strict original sense (Pellegrin, 1925: 465, as Carpodinus glandulosa Pellegr.); only three collections have been seen, of which McPherson 15106 is the first with fruits. It has long been confused with the much more frequent Landolphia obovata, and with another, undescribed species from Cameroon, represented by the specimens Letouzey 11153 and D.W. Thomas 4297. Apart from the type and these two Cameroonian collections, all specimens cited by Persoon et al. (1992) belong to L. obovata. Their descriptions include characters of the three species, while the line drawing entirely represents L. obovata. All three species share lenticellate stems, leaves gland-dotted below with widely spaced and ascending secondary veins, reticulate tertiary venation, congested axillary inflorescences, and moderately large corollas that are glabrous outside or pubescent only on the margin of the lobes; differences between them are summarised in Table 3.

Other specimens studied. – Gabon. Estuaire: S of Estuaire du Gabon along Remboué River, British Gas site, 0°12′S 10°01′E, 11.I.1991, fr., McPherson 15106 (BR, LBV, WAG); ibid. loco, fl., McPherson 15107 (LBV).

Holotypus: Gabon. Woleu-Ntem: Crystal Mountains, Tchimbélé, 0.5 km NE of dam, 19.III.1990, fl. & fr., Wieringa 713 (3-part specimen: WAG [WAG.1611082, WAG.1611083, WAG.1611084]!; iso-: BR [BR0000014305115]!, C, K, LBV [LBV0000704]!, MO, PRE).

Landolphia obovata O. Lachenaud & Jongkind is distinct from other species in the genus by its obovate leaves with a narrowly cordate base and conspicuous glandular dots on the lower surface, and its broadly obovoid fruits with a thick transverse ridge near the top.

Lianas up to 20 m long (at least). Branches greyish to dark brown with paler lenticels becoming very conspicuous on old branches; branchlets 2–4 mm thick, brown, pubescent to puberulous with short patent hairs or rarely glabrous. Leaves opposite; blade obovate, 4–14.5 × 2–7.5 cm, narrowly cordate or auriculate at base, obtuse to acuminate at apex with acumen ≤ 0.8 cm long, coriaceous and dark green when fresh, drying dark brown above and dark brown to olive green below, above glabrous or sparsely pilose at base of midrib, below sparsely pilose with erect hairs ≤ 0.2 mm long or sometimes puberulous on veins only, glandular dots conspicuous on lower leaf surface (1–5 per cm^2), blackish when dried; midrib impressed above, raised below; 6–8(–10) pairs of curved and conspicuously looping secondary veins; tertiary venation reticulate, prominent or not; petiole 2–10 mm, glabrous or pubescent like branches. Inflorescences 3–8-flowered, axillary, fasciculate or in highly contracted cymes; peduncle up to 4 mm long, densely tomentose; bracts triangular to narrowly obovate, 0.8–1 × 0.3–0.5 mm, acute to obtuse at apex, concave and thickened dorsally, tomentose outside, glabrous inside. Flowers 5-merous; pedicel 1–4 mm long, tomentose or pubescent; bracteoles 2, under calyx, similar to bracts. Calyx lobes imbricate, elliptic to broadly ovate, 1–1.5 times as long as wide, 2–2.5 × 1.3–2.2 mm, acute to rounded at apex, keeled and thickened at base, otherwise membranaceous, outside pubescent in central area and glabrous elsewhere, ciliate on margin, inside with basal colleters. Corollas pale green outside and white inside; tube 6–9 × 1–2 mm (at base), 2–2.5 mm around anthers and 1.5–2 mm at throat, glabrous outside, inside with very sparse hairs around insertion of stamens; lobes lanceolate, 9–17 × 2–4 mm, ciliate at least on basal auricle. Stamens c. 2 mm long, inserted towards upper 1/4 of tube, included; filaments 0.5 mm long; anthers 1.5 × 0.6 mm, acute at apex, glabrous, their apex almost reaching throat. Pistils 6.3–7.3 mm long; ovary c. 2 mm long, with glabrous cylindrical base 0.7 × 0.9 mm and pilose ovoid apex, 1.3 × 1.3 mm; style cylindrical, 3–4 mm long, glabrous; pistil head ellipsoid or oblong, 0.8 × 0.5–0.7 mm, more or less ciliate at apex; stigmoid apex cylindrical, 0.5–0.8 × 0.2–0.3 mm. Fruits glaucous green when young, orange when mature, broadly obovoid (length ≤ width), 4.6–8 × 5.6–8 cm in vivo, rounded or retuse at apex, near apex with a 1–2 cm wide transverse ridge, smooth or somewhat bumpy, 5–15-seeded, wall 0.5–1.5 cm thick, pulp orange with sweet taste. Seeds irregularly ovoid or ellipsoid, often laterally compressed, 18–23 × 13–17 × 10–13 mm; cotyledons (irregularly) ovate or elliptic, undulate.

Distribution, ecology and phenology. – This species occurs in the South Region of Cameroon, and in Gabon where it is relatively widespread in the western half of the country (but apparently absent along the coast); it should also be expected in Equatorial Guinea (Fig. 8B). It grows in primary and secondary forests, up to elevations of 535 m. Flowers have been collected from November to May (once in bud in September), i.e., most of the year except for the main dry season; fruits in January, March, June, September and November.

Conservation status. – Landolphia obovata occurs in lowland forests in Cameroon and Gabon and is known from 20 collections representing 18 localities. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 72 km^2, below the threshold for “Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) is calculated as 101,384 km^2, well above the threshold for “Vulnerable” status under Criterion B1. Two of its sites are located within a protected area, the Campo-Ma'an National Park in Cameroon. Most of the remaining sites are in forestry, oil and mining concessions and are therefore exposed to some level of habitat degradation due to these activities. However, in view of its relatively wide distribution (the 18 occurrences represent 16 locations in the sense of IUCN) the species is assessed as “Least Concern” [LC]. It is, furthermore, likely to be more widespread than records suggest.

Notes. – This species is rather distinctive, even in the vegetative state, by its obovate leaves with glandular dots and cordate base, and also by the shape of its fruits. It is relatively frequent, and has been well-represented in herbaria for a long time, but rather surprisingly Persoon et al. (1992: 78–79), in their otherwise excellent revision of African Landolphia, treated it as L. glandulosa (see additional comments under the latter species and Table 3 for differences). The specimen Leeuwenberg et al. 13588 was mistakenly cited as 12588 in their revision.

In addition to Landolphia glandulosa, this species could be mistaken for L. jumellei (Pierre ex Jum.) Pichon, which has leaves of a similar shape but lacking glandular dots and is generally much hairier, and L. dulcis (Sabine) Pichon (s.l.), which leaves are also frequently subcordate at base and gland-dotted, but more elliptic and either glabrous or with longer hairs; both species also have quite different flowers and fruits.

Additional specimens examined. – Cameroon. South Region: TDC, 10.XII.1991, fl., F. Hallé 4336 (P, WAG); km 48 route Sangmélima-Yaoundé, Mvoutessi I, 17.XII.1986, fl., Lejoly 86/1107 & Lisowski B-3587 (BR); W of the recently reconstructed road from Ebolowa to Minkok, on bank of fast streaming creek, fr., 6.VI.1975, J.J.F.E. de Wilde 8275A (BR, MO, WAG); Campo Reserve, near the village Ebianemeyong, bank of Ntem River, 11.XII.1998, fl., J.J.F.E. de Wilde et al. 12148 (WAG).

Gabon. Estuaire: Concession SEEF, 0°31′N 10°41′E, 2.XI.2017, fl. bud & fr., Bidault et al. 3497 (BR, BRLU, MO, P, WAG). Moyen-Ogooué: zone de Mabounié, à 45 km au sud-ouest de Lambaréné, rive nord de la rivière Ngounié, 13.XI.2013, imm. fr., Bidault et al. 1272 (BR, MO, P, WAG); zone de Lambaréné, à 50 km au sud de la ville, à 15 km au sud-est du lac Ezanga, 22.XI.2013, imm. fr., Bidault et al. 1398 (MO, P, WAG); Mabounié, between the Ngounié River and the camp, 7.V.2012, fl. bud, Stévart & Droissart 4402 (LBV, MO, WAG); near Bellevue, 9.VI.1987, fr., D.W. Thomas 6651 (BR, LBV, MO, WAG). Ngounié: Fougamou, 16.II.1924, fl., Le Testu 6390 (BR, P, WAG). Ogooué-Maritime: Rabi, 31.III.1990, fl., Breteler et al. 9691 (BR, LBV, P, WAG); 30 km S of Rabi, near Echira River, 28.XI.1989, fl. & imm. fr., J.J.F.E. de Wilde et al. 9831 (BR, LBV, WAG). Nyanga: along a forest exploitation track near the Doussa River, 7.XII.1986, fl. bud, J.J.F.E. de Wilde et al. 9208 (BR, LBV, P, WAG). Woleu-Ntem: 30 km of Abanga R. to the east, 15.IX.1985, fl. bud & imm. fr., Leeuwenberg et al. 13549 (BR, LBV, P, WAG); S of Medouneu, 40 km E of SEF Camp, 17.IX.1985, fl. bud & fr., Leeuwenberg et al. 13588 (BR, LBV, P, WAG); c. 15 km NW of forestry camp Oveng, 8.II.1987, fl. bud., Reitsma & Reitsma 2934 (LBV, WAG); Crystal Mountains, 1.5 km NE of Tchimbélé, 5.I.1990, imm. fr., Wieringa 358 (BR, C, K, LBV, MO, PRE, WAG); 0.5 km E of Tchimbélé, 27.IV.1990, fl., Wieringa 780 (BR, C, LBV, MO, WAG).

Holotypus: Gabon. Ngounié: Site Ramsar de Birougou, 20 km au N de Malinga, village Mbomo, rive Est de la Bibaka, 2°16′49″S 12°13′53″E, 669 m, 20.III.2018, fl., Bidault et al. 3927 (MO!; iso-: BR!, BRLU [BRLU0027468]! + spirit!, LBV!, P!, WAG!).

Landolphia persooniana O. Lachenaud & Jongkind resembles L. subrepanda (K. Schum) Pichon in its congested axillary inflorescences, leaf midrib channelled above and secondary veins inserted almost at a right angle, corolla pubescent outside with a tube 5.5–8 mm long, anthers acute at apex, ovary pilose at apex, style glabrous and long tapering pistil head, but has corolla lobes 9.5–18 mm long and exceeding the tube (vs. 2.8–6.9 mm long, shorter than tube).

Lianas at least 12 m long, with tendrils and white latex. Twigs 1–2.5 mm thick, grey to dark brown, sparsely hirsute or sometimes densely hairy, with inconspicuous brown lenticels. Leaves opposite; blade elliptic, 4–10 × 1.3–4.7 cm, base rounded to slightly narrowly cordate near petiole, apex abruptly acuminate to caudate for 1–1.5 cm, coriaceous, glossy, dark green above, beneath dark green with pale green midrib, glabrous or with very sparse hairs on midrib below, glandular dots conspicuous on lower leaf surface (2–5 per cm^2), blackish when dried; midrib channelled above; 8–15 pairs of almost straight secondary veins, inserted at an almost straight angle to midrib, alternating with (slightly) fainter parallel intersecondary veins and forming conspicuous loops 1–2.5 mm from leaf margin; tertiary veins rather laxly reticulate and not very conspicuous below; petiole 2–7 mm long, sparsely hirsute. Inflorescences axillary, subsessile, cymose and highly contracted, 1–10-flowered, bracts ovate, c. 0.5 mm long, appressed hairy outside, glabrous inside. Flowers 5-merous, fragrant; pedicel 1–1.5 mm long, with sparse and short appressed hairs, 2 bracteoles at apex of pedicel; flower bud up to 21 mm long. Calyx lobes imbricate, narrowly ovate to triangular, 1–1.5 × 0.5–1 mm, acute to obtuse at apex, ciliate and sparsely pubescent outside on exposed parts, light green. Corollas pale greenish yellow; tube 5.5–8 × 1–1.2 mm, slightly inflated around stamens, densely pubescent with short ascending hairs outside, inside sparsely hairy from insertion of stamens to throat; lobes linear, 9.5–18 × 0.5–2 mm, glabrous or with very sparse hairs on margin, white. Stamens included, inserted slightly above middle of tube, filaments c. 1 mm long, glabrous, anthers 1.8–2 mm long, glabrous or with a few hairs on back and with a tuft of hairs at apex; pistil 4.5–5 mm long, ovary c. 0.8 mm long, cylindrical, glabrous at base and villose at apex, style 2.5–2.7 mm long, glabrous; stigmatic head 1.2–1.5 mm long. Fruits unknown.

Etymology. – This species is named after Johannes (Hans) G.M. Persoon, previous monographer of African Landolphia, who recognised its first collection as possibly new in 2013.

Distribution, ecology and phenology. – Endemic to the Mayombe and Chaillu massifs in southern Gabon (and probably adjacent Republic of Congo) (Fig. 8A), occurring in secondary forest edges, and secondary forests near rivers, at elevations of 90–740 m. All three specimens in flower have been collected in March, during the short dry season.

Conservation status. – Landolphia persooniana is endemic to Gabon and occurs in low- to mid-altitude evergreen forests; it is known from three collections representing three distinct localities. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 12 km^2, which falls under the threshold for “Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) is calculated as 7,696 km² which falls under the threshold for “Vulnerable” status under Criterion B1. The three known occurrences represent three subpopulations. None of them are included within protected areas. Two localities are within logging concessions; whether this represents a threat to the species is unclear, since little is known of its ecological requirements and many liana species (including other Landolphia) may actually benefit from moderate levels of forest disturbance. The species is also likely to be undercollected since it is a tall liana, flowering high in the canopy. With the limited data available at this moment, and using the IUCN criteria, we cannot reach a realistic threat category, and therefore L. persooniana is included in the “Data Deficient” [DD] category.

Notes. – In most of its characters this species is very close to Landolphia subrepanda (Fig. 9A–C), but the corolla proportions are quite different (see diagnosis above). The leaves of L. subrepanda are quite variable but tend to be larger (usually > 10 cm long), often more obovate, with the lateral veins more pronounced than in L. persooniana, and almost always lack glandular dots on the lower side (exceptionally these are present in Le Testu 6353). It is not known if there are additional differences in the fruits, since those of L. persooniana have not been collected.

The new species also resembles Landolphia anthonii, L. ferrea and L. glabra, which have quite similar leaves, inflorescences, and corolla lobes, but differs from all by its pilose twigs and its corolla tube which is pubescent outside (Table 2); the corolla tube and style are also much longer than in L. anthonii. Finally, it also resembles L. robustior (K. Schum.) J.G.M. Pers. in its inflorescences and flowers, but the latter has glabrous twigs with peeling bark, leaves lacking glands and intersecondary veins, with lateral veins more ascending and the midrib flat or prominent above, and the corolla tube glabrous inside and pubescent inside for most of its length (only above stamen insertion in L. persooniana).

Additional specimens examined. – Gabon. Ngounié: 22 km on the road Moukabou to Mbigou, 1°40′S 11°47′E, 740 m, 15.III.2013, fl., Wieringa et al. 7454 (WAG! + spirit!). Nyanga: Région de Kaye au sud du Massif du Mayombe, 3°38′33″S 11°09′44″E, 31.III.2012, fl., Boupoya et al. 685 (BRLU!, LBV, MO).

Holotypus: Gabon. Ngounié: collines au sud-est du Lac Ezanga, 1°10′S 10°19′E, 100 m, 21.XI.2013, fr., Lachenaud et al. 1518 (2-part specimen: BRLU [BRLU0024324]! + spirit!; iso-: BR [BR0000024390620]!, LBV!, MO-6910313, P, WAG [WAG.1963405]!).

Landolphia verrucosa Jongkind & O. Lachenaud resembles L. owariensis and L. mannii Dyer with its terminal and densely cymose inflorescences, leaves with secondary veins forming conspicuous loops and much more prominent than the densely reticulate tertiary venation, and medium-sized corolla with lobes shorter than the tube. It differs from both species by the folded and twisted ridges on the fruit, and the usually subcordate (vs. acute to rounded) leaf base. It is further separated from L. owariensis by its corolla that is completely glabrous inside (vs. pubescent in the throat) and from L. mannii by its corolla lobes that are pubescent outside on the whole surface (vs. glabrous on the part covered in bud).

Lianas up to 30 m long, exuding white latex. Branchlets 2–4 mm thick, dark brown with pale lenticels, shortly velutinous with ± curly hairs. Leaves opposite; blade (3.5–)6.5–15 × (2–)3.8–6.5 cm, elliptic to slightly obovate, subcordate or rarely rounded at base, gradually narrowing into a short acumen or rarely obtuse at apex, papery, drying dark brown to greyish above and pale grey-brown below, usually glabrous above except minutely puberulous veins, below densely tomentose on veins and with very sparse short hairs between them (denser on very young leaves), glandular dots absent; midrib impressed above, raised below; 9–15 pairs of secondary veins, slightly impressed above and very prominent below, inserted at a very broad angle to midrib and ending in a conspicuous looping intramarginal vein 2.5–5 mm from margin; tertiary venation reticulate, dense but not prominent, conspicuously darker in vivo, forming areolae c. 0.5 mm in diam.; petiole 3–7 mm long, pubescent like twigs. Inflorescences terminal, cymose, 2–5 cm long, many-flowered, usually clearly but shortly branched, sometimes longer and slightly tendril-like, velutinous; peduncle up to 0.5 cm long; bracts broadly ovate, 1.5–2.5 × 1–2 mm, acute at apex and slightly carinate dorsally, velutinous outside, glabrous inside, caducous. Flowers 5-merous, with velutinous bracteoles embracing calyx; pedicel 1–2 mm long, velutinous. Calyx lobes broadly ovate, c. 2 × 1.7–3 mm, rounded at apex, velutinous. Corollas more or less succulent, brownish outside, dark cream coloured inside, tube c. 7 × 3 mm, almost cylindrical, velutinous outside, glabrous inside, lobes 8–9 × 3 mm, first erect then bending outward, entirely velutinous outside but less densely than tube, appressed hairy inside. Stamens included, subsessile, inserted at 3.5–4 mm above base of corolla; anthers 1.5 mm long, glabrous. Pistils 2.5–3 mm long, not reaching anthers. Fruits subglobose to obovoid, c. 4 cm in diam., surface folded in twisting ridges and bumps, very pale green or brown (probably not fully mature), glabrous. Seeds not seen.

Distribution, ecology and phenology. – This taxon is endemic to Gabon (Estuaire, Moyen-Ogooué and Ngounié provinces; Fig. 8A) and occurs in wet evergreen lowland forests, at elevations of 60–80 m. Flowers have been collected in April, and fruits in November.

Conservation status. – Landolphia verrucosa is endemic to Gabon and occurs in lowland evergreen forests; it is known from three collections representing three distinct localities. Due to the recent dates of collection, we consider that all of the recorded occurrences are extant. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 12 km^2, which falls under the threshold for “Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) is calculated as 7,677 km^2, which falls under the threshold for “Vulnerable” status under Criterion B1. The three occurrences represent three subpopulations. None of the sites are within protected areas. Two of them are in current logging concessions; whether this represents a threat to the species is unclear, since little is known of its ecological requirements and many liana species (including other Landolphia) may actually benefit from moderate levels of forest disturbance. The species is also likely to be under collected since it is a tall liana, flowering high in the canopy. With the limited data available at this moment, and using the IUCN criteria, we cannot reach a realistic threat category, and therefore L. verrucosa is included in the “Data Deficient” [DD] category.

Notes. – Landolphia verrucosa closely resembles the much more common and widespread L. owariensis and L. mannii, especially in the flowering stage, but differs by the characters mentioned in the diagnosis. Its earliest collection, Louis et al. 271, was cited under L. owariensis by Persoon et al. (1992: 221). The characteristic ornamentation of the fruits of L. verrucosa is unique among Central African Landolphia (though fruits of a few species are unknown yet). The West African Landolphia nitidula J.G.M. Pers. also has verrucose fruits, but is otherwise a very dissimilar species because of its glabrous, obovate leaves and axillary inflorescences.

The characters of the pistil of Landolphia verrucosa remain partly unknown, due to insect damage on the only open flower available.

Additional specimens examined. – Gabon. Estuaire: c. 7 km E of N'Voum, 24 km NE of Ntoum, 1.XI.1983, fr., A.M. Louis et al. 271 (LBV, WAG). Moyen-Ogooué: 5–30 km NNW of Ndjolé, 27.IV.1992, fl., Breteler et al. 11133 (BR, K, LBV, S, WAG).

Oncinotis

The genus Oncinotis is closely related to Baissea (see above) and Motandra, which it resembles very much in fruit and vegetative characters. It differs from both by the presence of five coronal appendages in the corolla throat between the lobes, and from Baissea also by its anthers with curved and obtuse basal tails. Oncinotis was revised by de Kruif (1985) and has eight species (including the new species described here), seven of which are found in continental Africa and one in Madagascar. Differences between the six Central African species of Oncinotis are presented in Table 4. The remaining continental species is the West African O. nitida Benth., easily recognised by its numerous secondary leaf veins (13–25 pairs).

Holotypus: Gabon. Ogooué-Lolo: Bambidie, c. 30 km E of Lastoursville, 10.VIII.2000, fl., F.J. & B.J.M. Breteler 15574 (2-part specimen: WAG [WAG.1662404]! + spirit!; iso-: LBV!, MO).

Oncinotis gabonica O. Lachenaud differs from its congeners by its relatively long corolla tube (4–5 times as long as the calyx) and short lobes (the tube/lobes ratio about 2:1) and its almost glabrous leaves with conspicuous tuft domatia in the main vein axils and dense subparallel tertiary veins. Other species of Oncinotis have the corolla tube 1–3.5 times as long as the calyx, the corolla lobes 0.7–2 times as long as the tube, the leaves either villose below or if glabrous with domatia of the pit type (or absent), and the tertiary leaf veins laxer and usually reticulate.

Lianas woody with slender stem. Branchlets cylindrical, 1 mm thick, with short and moderately dense fulvous indumentum of simple crisped hairs c. 0.3 mm long. Leaves opposite; blade narrowly obovate to narrowly elliptic, 9–15.5 × 3.6–5.3 cm, acute at base, abruptly acuminate for 0.8–1.2 cm at apex, thinly papery, glabrous except domatia and very sparse simple hairs on midrib and secondary veins below, drying olive green; midrib impressed on upper side, prominent below; secondary veins 7–11 pairs, strongly curved and forming prominent loops 2–3 mm from leaf margin; tertiary veins dense, subparallel, prominent and concolorous on lower leaf surface; domatia present as conspicuous tufts of rufous hairs in main vein axils; petiole 0.5–1 cm long, pubescent on upper side with same indumentum as twigs and bearing a pair of colleters at junction with leaf blade, glabrous on lower side. Inflorescences axillary and paired at nodes, thyrsoid, 1.5–3.4 cm long, with indumentum similar to twigs but denser; peduncle 0.5–1.5 cm long, rachis 0.7–1.2 cm long, main branches 0.2–0.5 cm long; bracts minute, narrowly triangular, 0.5–1.2 × 0.2–0.5 mm, pubescent. Flowers 5-merous; pedicel 1–2 mm long, with short fulvous crisped hairs. Calyces purplish, with 5 imbricate ovate lobes, 1–1.2 × 0.5–0.7 mm, obtuse to subacute at apex, pubescent outside, glabrous inside. Corollas purplish outside and pale brownish-green inside; tube narrowly infundibuliform, 4–5 × 1.8–2 mm, slightly constricted at apex, covered outside (except at very base) with short patent or slightly retrorse hairs, villose inside with slightly retrorse hairs from insertion of stamens to throat; lobes overlapping to right, narrowly elliptic, 2–2.5 × 0.7–1 mm, rounded at apex, pubescent outside like tube on part exposed in bud, glabrous inside; flower bud fusiform, obtuse at apex; throat with 5 erect appendages 0.5–0.8 × 0.2 mm, alternating with lobes. Stamens fully included, inserted c. 1 mm above base of corolla tube, subsessile; anthers 2.3 × 0.4 mm, basally with rounded caudicles, acuminate at apex, glabrous. Pistils included; ovaries ± cylindrical, 0.7 mm long, pubescent at apex, 2-carpellate; disk annular, 0.5 mm high, glabrous; styles included, 1.5 mm long, glabrous, fusiform and inflated in median part, attenuate at apex and shortly bifid for 0.25 mm. Fruits unknown.

Distribution, ecology and phenology. – Only known from the type locality in east-central Gabon (Fig. 8B), where it was collected once in secondary lowland evergreen forest. Its area of origin is relatively well-explored, and in the absence of further records the species is certainly rare in that area. Flowers have been collected in August, during the main dry season.

Conservation status. – This species is known from a single collection that represents one occurrence and one population. Due to the important forest cover in the area, we consider this occurrence as extant. Based on a 2 × 2 km cell size, its Area of Occupancy [AOO] is estimated as 4 km^2, which falls under the threshold for “Critically Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) cannot be calculated. The only known occurrence is located within an active logging concession. It is unclear whether logging itself represents a current threat to the species, since little is known of its ecological requirements, and many liana species (including other Oncinotis) may benefit from moderate levels of forest disturbance. However, considering the species' apparently very restricted range, other activities related to the concession (such as the building of roads or other infrastructures) may represent a future threat. Oncinotis gabonica is therefore assessed as “Vulnerable” [VU D2].

Pleiocarpa

The genus Pleiocarpa belongs to tribe Hunterieae (Endress et al., 2018) and is closely related to Hunteria (see above) and Picralima. It was revised by Omino (1996) together with these two genera, from which it differs by the absence of colleters inside the sepals, the pistil head which is subglobose to oblong without a stigmoid apex, and the 2–5-carpellate ovaries (vs. always 2-carpellate).

The genus is restricted to tropical Africa and includes seven species, including the one described here. Despite its small size, it is quite difficult taxonomically, since some of the species are very variable and difficult to separate; however, the new species is a well-defined one, which characters are quite constant. Another new species of Pleiocarpa occurs in Gabon, but is represented by fruiting material only (Lachenaud et al. 2567); it differs from other Pleiocarpa by its suffrutescent rhizomatous habit, and smooth, narrowly ovoid, rostrate monocarps. More material is needed before it can be described.

Holotypus: Gabon.Ogooué-Lolo: right bank of Ogooué R. near Lastoursville, c. 0°50′S 12°41′E, 21.IX.1970, fl. & imm. fr., Breteler 6558 (BR [BR0000014550201]!; iso-: LBV!, WAG [WAG.1620439, WAG.1620438, WAG.1620437]! + spirit!).

Pleiocarpa robusta O. Lachenaud resembles P. mutica Benth. in its uniovulate carpels, otherwise not found in the genus, and in corolla characters, but has secondary leaf veins prominent and strongly curved (vs. very weak and almost straight) and fruits covered with small domed warts, while those of P. mutica are smooth in vivo and minutely wrinkled when dried. It also resembles P. rostrata Benth., especially in vegetative characters, but the latter species has 3–4(–6) ovules per carpel and larger fruiting mericarps, 20–50 × 15–25 mm as opposed to (9–)15–18 × 7–11 mm in P. robusta.

Shrubs 1–2 m tall, branched, with white latex. Twigs glabrous, 1–2.5 mm thick, blackish, ± angled and longitudinally striate when dried, somewhat lenticellate. Leaves glabrous; blade elliptic, 12.5–25 × 3.8–11.5 cm, acute at base, abruptly caudate for 1.5–3 cm at apex, coriaceous, slightly shiny, drying olive green to greyish above, pale grey-green to olive-brown below; midrib prominent in centre and sulcate laterally on upper side, prominent on lower side; secondary veins 6–14 pairs, well-marked and conspicuous, moderately ascending, bullate above and strongly prominent below, anastomosing < 1 mm from leaf margin; tertiary veins forming a transversely stretched network, rather dense and prominent above in dry state, laxer and less conspicuous below; petiole 0.7–1.7 cm long, wrinkled when dried, upper side canaliculate with margins almost touching each other. Inflorescences terminal or axillary, glomerulate, sessile, 4–10-flowered; bracts minute, ovate, 1–1.8 × 0.8–1.2 mm, rounded at apex, glabrous. Flowers 5-merous, fragrant; pedicel 0–1 mm, glabrous. Calyces glabrous, divided almost to base, lobes imbricate, elliptic to ovate, 1.5–1.8 × 1.3 mm, rounded or obtuse at apex, without colleters inside. Corollas white; tube 15–16 × c. 1 mm (at mid-height), slightly swollen at base (1.5 mm broad) and at apex (1.3 mm broad) which is ± pentagonal, glabrous outside, papillose inside around stamens and sparsely villose for c. 6 mm below their insertion; lobes narrowly elliptic, 5–6 × 2–3 mm, laterally auriculate at base, rounded at apex, overlapping and contorted to left, glabrous on both sides. Anthers included, sessile, inserted c. 2 mm below mouth of tube with their apex almost reaching throat, narrowly ovate, c. 1.6 × 0.8 mm, acute or obtuse at apex, glabrous. Pistils included, reaching just under base of stamens; ovaries glabrous, with 5 carpels c. 1 × 0.4 mm, uniovulate; styles c. 12 mm long, glabrous; stigma swollen, ovoid, c. 1 mm. Fruits dark green when young, orange when mature, with 5 free carpels, these obovoid to ellipsoid, (9–)15–18 × 7–11 mm, acute at apex, glabrous, surface densely covered with domed warts, sometimes with irregular larger warts. Seeds obovoid, one per carpel, c. 11 × 6.5 mm.

Distribution, ecology and phenology. – This species is endemic to Gabon, where it is restricted to the middle Ogooué valley between Ndjolé and east of Lastoursville; it appears to be rare in the west of its range, but relatively frequent in the east (Fig. 6). It occurs in lowland evergreen forests on drained soils, at elevations of 250–500 m. Flowers have been collected in January, July and September-October; immature fruits from September to January, mature from March to May.

Conservation status. – Pleiocarpa robusta is endemic to Gabon and occurs in lowland evergreen forests; it is known from 16 collections representing 16 localities. All occurrences are considered still extant, due to the recent dates of collection and the important forest cover still present in the areas. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 64 km^2, which falls under the threshold for “Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) is calculated as 9,032 km^2, which falls under the threshold for “Vulnerable” status under Criterion B1. The 16 occurrences represent 4–7 subpopulations. None of them are included within protected areas, but the species is likely to be present in Lopé and Ivindo National Parks, since it has been collected not far from their borders. Most of the occurrences (15) are located within logging concessions, one occurrence near Ndjolé is not included in a concession, but was collected near an access road. All the 16 sites are threatened by logging, which suggests a decline of the extent and quality of habitat of this species. Two of them, which are in the same logging concession near Booué, are additionally threatened by a road building project, which is expected to cause a decline in the extent and quality of habitat and number of individuals; they represent a single location (sensu IUCN). The occurrence near Ndjolé represents another location. Three occurrences are included into three different logging concessions, and therefore represent three different locations. Ten occurrences are located within a single logging concession, east of Lastoursville; one is in a conservation zone within the concession and represents one location, the other are in exploited areas and represent a second location. Consequently, the 16 occurrences represent seven locations, with regard to the most serious plausible threat (logging). We infer a past, present and future continuing decline of the extent and quality of the habitat of this species and number of individuals. Pleiocarpa robusta therefore qualifies for “Vulnerable” [VU B1ab(iii,v)+2ab(iii,v)].

Notes. – This species has previously been mistaken for Pleiocarpa mutica, from which it differs by the characters mentioned in the diagnosis like the small domed warts on the fruit carpels (Fig. 9E, F); it is also generally more robust in all its parts (hence the specific name) but the dimensions overlap widely. The maximum size of the leaves of P. mutica (29.5 × 11.4 cm), as well as those of the corolla tube (22 mm long), lobes (13 × 4.3 mm) and style (16 mm long) mentioned in the description by Omino (1996: 142), presumably refer to another taxon, since we found these dimensions to be consistently smaller in P. mutica s.str. (see Table 5). From the three Gabonese collections cited under P. mutica by Omino (1996: 146), two are P. robusta (Breteler 6558 and 13338) while the third is P. brevistyla Omino (Breteler & van Raalte 5635). Three other specimens, McPherson 17968, Nguema Miyono 1879 & Wieringa 856, two of them collected after the revision, are now representing P. mutica for Gabon. Pleiocarpa mutica occurs from Sierra Leone to Gabon and appears to reach its southern limit in the Monts de Cristal in north-western Gabon; its range is thus separate from that of P. robusta, which occurs in central and east-central Gabon.

The identity of a single fruiting collection from south Cameroon, J.J.F.E. de Wilde 8150A, is uncertain for the moment since it resembles Pleiocarpa robusta in fruit ornamentation but P. mutica in leaf characters; complementary material is needed to solve its status.

In addition to Pleiocarpa mutica, the new species may be confused with P. rostrata and Hunteria hexaloba that are both very similar in vegetative characters, and with Pleiocarpa picralimoides (Pichon) Omino; differences between all these taxa are summarised in Table 5. It must be noted that P. rostrata, as currently delimited, is exceedingly variable in the size of its flowers and fruits, and in the shape and ornamentation of the latter; it may quite probably consist of more than one taxon. The main range of P. rostrata is in Nigeria and Cameroon; a single collection from Gabon, Le Testu 8871, cited by Omino (1996), appears to be correctly identified, though quite distant geographically from the rest and occurring within the range of P. robusta (from which it differs by its pluriovulate carpels and larger corolla).

Additional specimens examined. – Gabon. Moyen-Ogooué: 15 km NE of Ndjolé, 0°07′S 10°49′E, 31.I.1991, fl. bud, de Wilde & Sosef 10323 (LBV, WAG). Ogooué-Ivindo: 3 km SE de Booué, 0°08′S 11°57′E, 13.VI.1987, fl., Wilks 1574 (WAG); Forêt des Abeilles, autour du camp 1, concession forestière CFAD, 0°08′S 11°58′E, 21.II.2021, fr., Paradis et al. 302 (MO). Ogooué-Lolo: c. 30 km NE of Lastoursville, forest exploitation on right bank of Ogooué River, 12.IV.1990, fr., Breteler et al. 9898 (WAG); c. 30 km E of Lastoursville, road to l'Ogooué, 7.V.1992, fr., Breteler et al. 11358 (WAG + spirit); c. 14 km NE of Bambidie, 17.X.1994, fl. bud, Breteler et al. 13338 (WAG); Bambidie, c. 30 km E of Lastoursville, 0°44′S 12°58′E, 9.XI.1999, imm. fr., Breteler 15421 (BR, LBV, WAG); Forêt des Abeilles, Station de la Makandé, 0°40′39″S 11°54′35″E, 1.XI.1996, imm. fr., Doucet 448 (BR); E of Lastoursville, near Bambidie, C.E.B. chantier, 0°46′S 13°03′E, 21.IX.1996, fl. buds, McPherson 16660 (BR, LBV, WAG); E of Lastoursville, near Bambidie, C.E.B. chantier, 0°46′S 13°00′E, 23.IX.1996, fl., McPherson 16669 (LBV); Bambidi, axe Lastoursville-Ndangui, 0°45″S 12°58″E, 21.V.2003, fr., Nziengui et al. 518 (LBV); environs du village Vouboué, Forêt des Abeilles, 29.VIII.1983, fl., Sita 5177 (LBV); Concession CEB, Réserve de Milolé, 0°36′52″S 12°47′17″E, 15.III.2017, fr., Texier et al. 913 (BRLU, MO); 33 km ENE of Lastoursville, 6 km on CEB exploitation road B, 0°42′S 13°0′E, 14.XI.1994, imm. fr., Wieringa et al. 3175 (WAG); c. 30 km ENE of Lastoursville, 15 km on forestry road from Bambidie to Akieni, 0°39′S 12°56′E, 29.I.2008, imm. fr., Wieringa et al. 6262 (BR, LBV, MO, WAG).

Tabernaemontana

Tabernaemontana is a pantropical genus of more than 120 species of trees, shrubs and lianas, and belongs to tribe Tabernaemontaneae, subtribe Tabernaemontaninae (Endress et al., 2018). The genus is closely related to Voacanga, both having in common a dichotomous branching pattern, petioles connate at base into a short ochrea, corolla lobes contorted to the left, absence of a corona, anthers included or with only the very tip exserted and tailed at base, fleshy fruits with two usually separate carpels, and arillate seeds. The two genera differ by their corolla lobes which are inflexed in bud in Tabernaemontana vs. not inflexed in Voacanga, the pistil head which is free from the anthers in Tabernaemontana vs. coherent with the anthers (and therefore shed with the corolla) in Voacanga, and the calyx which is persistent in Tabernaemontana and caducous in Voacanga.

The Old World species of Tabernaemontana were revised by Leeuwenberg (1991), who recognised 18 species in continental Africa. A new West African species, previously misidentified as T. psorocarpa (Pierre ex Stapf) Pichon, is described here.

Holotypus: Liberia. Gbarpolu: 9 km E of Yoma, 20 km NE of Bomi Hills, fl., 6.VIII.1962, Leeuwenberg 4881 (2-part specimen: WAG [WAG.1672632, WAG.1672633]!; iso-: B, BR [BR0000014349065]!, EA, HBG, K!, MO, P [P04256880] image!, UC).

Tabernaemontana fragrans Jongkind resembles T. psorocarpa (Pierre ex Stapf) Pichon in its climbing habit, relatively small flowers, and inflorescences with a distinct peduncle (0.5–4 cm long) but differs by its more narrowly ovoid fruits that are yellow to orange at maturity and angled to narrowly winged (vs. bumpy and pale bluish-green, not winged), its calyx lobes not longer than broad (vs. distinctly so) and its slightly larger corolla with a tube 13–18 mm long and lobes 13–20 mm long, the latter pubescent only on the left margin (vs. tube 9–14 mm long and lobes 7–17 mm long, the latter puberulous on both sides towards the base).

Lianas at least up to 20 m long, twining, latex white. Branchlets glabrous. Leaves of a pair equal or sometimes unequal, glabrous; blade 6–15 × 1.2–5.5 cm, elliptic to narrowly oblong, acute at base, acuminate at apex, dark green above, pale glaucous-green below; midrib prominent above; 6–9 pairs of hardly prominent secondary veins; tertiary venation inconspicuous; petiole 4–20 mm long. Inflorescences terminal (often becoming lateral due to sympodial growth of twigs) and usually paired, in umbelliform cymes, 3–10-flowered, glabrous; peduncle 5–40 mm long; bracts deciduous. Flowers 5-merous, with sweet scent; pedicel 8–19 mm long, glabrous. Calyces greenish, lobes round to broadly ovate, 2–2.5 × 2–2.5 mm, ciliate. Corollas white, glabrous outside, in bud lobes forming a comparatively wide ovoid or subglobose head with a blunt apex; tube 13–18 × 4 mm, ± cylindrical with inflated base, slightly twisted or not, inside with rather sparse hairs from insertion of stamens to throat; lobes 13–20 × 4–5.5 mm, lanceolate, ciliate on left margin, otherwise glabrous. Stamens included, inserted 3–4 mm above base of corolla tube; anthers c. 5 mm long, glabrous. Pistils 4–6 mm long, glabrous, reaching base of anthers; ovary cylindrical, c. 1.5 mm long, with two separated carpels; style c. 1.7 mm long, linear; pistil head 1.5–1.8 mm long, with a ring at base. Fruits of two separate and widely divergent mericarps, each up to 7 × 4.5 cm, narrowly ovoid and dorsoventrally compressed, with 3 narrow wing-like ridges, otherwise smooth, glabrous, yellow to orange.

Distribution, ecology and phenology. – This species is found in south-eastern Guinea, Liberia, Côte d'Ivoire and Ghana in forest up to elevations of 580 m (Fig. 15A). It is not known from the drier, semi-deciduous forests in Côte d'Ivoire and Ghana. Flowers have been collected mostly from June to December, once in March; fruits in November-December and March-April.

Conservation status. – The Extent of Occurrence (EOO) of Tabernaemontana fragrans is estimated as 129,500 km^2, well above the threshold for “Vulnerable” status under Criterion B1. It is known from c. 19 subpopulations. Based on a 2 × 2 km cell size, its Area of Occupancy (AOO) is estimated as 60 km^2, below the threshold for “Endangered” status under Criterion B2. The main threat to this species is from the ungoing clearance of forests for agriculture, plantations and mining in all four countries where it is found. A very substantial part of the forests in these countries is already gone (CILLS, 2016) and on several places where the species was collected there is no forest anymore today. However, the number of subpopulations is almost surely an underestimation since most of its range in Liberia is hardly explored. Tabernaemontana fragrans is known from several forest reserves and it is also likely to occur in protected areas like Taï National Park and Sapo National Park. It is also known to grow in secondary forests. The species is here assessed for the moment as “Near Threatened” [NT] because of the ungoing clearance of the forests, even in some of the protected areas, using the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – In the flowering stage this species closely resembles Tabernaemontana psorocarpa, and most of its collections were included by Leeuwenberg (1991) in the latter, which was supposed to have a disjunct distribution between West and Central Africa. The fruits of West African specimens, treated here as T. fragrans, are however quite different from those of Central African specimens, including the type of T. psorocarpa (Fig. 14A, B), and there are also more subtle differences in the flowers (Fig. 14D, F). On the other hand, fruiting specimens of T. fragrans resemble T. glandulosa (Stapf) Pichon (Fig. 14A, C), the only other climbing Tabernaemontana species occurring in western Nigeria, which has much larger flowers (Fig. 14E). The differences between the three species are summarised in Table 6.

In the revision of Old World Tabernaemontana (Leeuwenberg 1991: 62, fig. 15) the depicted fruits of T. psorocarpa s.l. are mixed and presented as mature and immature fruits from the same plant. After studying the spirit material kept at WAG it became clear that the “immature” fruit in this illustration corresponds to T. fragrans (Leeuwenberg 12100) from Côte d'Ivoire, while the “mature” fruit corresponds to T. psorocarpa s.str. (J.J.F.E. de Wilde et al. 23/83) from Gabon. The photograph on the next page of the revision (Leeuwenberg 1991: 63, photo 3), showing fruits of Leeuwenberg 11440, is from another Tabernaemontana species, currently under study.

Additional specimens examined. – Ghana. Western Region: Subiri Forest Reserve, Daboase, 4.VI.1974, fl., Enti 1348 (BR, WAG); Ankasa River Forest Reserve, 15.VII.1995, fl., Harder et al. 3462 (MO, WAG); Axim, III.1934, fr., Irvine 2395 (GC, K); Awiabo, XI.1928, fl., Vigne FH 1467 (GC, K, P).

Côte d'ivoire. Agnéby: 10 km E of Yakassé Mé, 15.IV.1980, imm. fr., Leeuwenberg 12100 (BR, K, MO, PH, S, WAG); Forêt de Yapo, 2.XI.1981, fl. & fr., Leeuwenberg 12277 (WAG). Bas-Sassandra: 25 km SW of Guéyo, 29.III.1962, fl., Leeuwenberg 3774 (BR, P, WAG).

Liberia. Gbarpolu: Gola Forest, 1.XII.2005, fr., Jongkind et al. 7062 (BR, WAG); Yeh River, 3.2 km above junction with St. Paul River, fl., 9.X.1926, Linder 999 (A, K, P). Nimba: versant oriental Nimba, 9.X.1969, fl., Adam 24113 (MO, P); route du Mont Tokadeh, 10.X.1971, fl., Adam 26262 (MO, P); Yuelliton Road, 19.X.1964, fl., Adames 665 (K, P, UPS); Ganta, 17.IX.1947, fl., Baldwin 9300 (K, MO); Tappeta area, 19.IX.1965, fl., P.P.C. van Meer 175 (BR, WAG). Sinoe: E of Greenville-Zwedru road, 26.IX.2013, fl., Jongkind et al. 12158 (BR, K, MO); N of Sapo National Park, 27.IX.2013, fl., Jongkind et al. 12167 (BR, FHO, K, MO, P).

Guinea. Nzérekoré: Nimba Mountains, 23.IX.2017, fl., Bidault et al. 3274 (BRLU, K, MO, P, SERG); Nimba Mountains, Forêt de Gbié, 17.XII.2008, fl., Haba & Bilivogui 19 (WAG); Nimba mountains, near Tuo, 6.VII.2008, ster., Nimba Botanic Team WD 489 (WAG).

Voacanga

Voacanga is a Paleotropical genus of trees and shrubs, belonging to tribe Tabernaemontaneae, subtribe Tabernaemontaninae (Endress et al., 2018) and closely related to Tabernaemontana (see above). The genus was last revised by Leeuwenberg (1985), who recognised 12 species, seven of which occur in Africa (one of them also in Madagascar) and five in Asia.

Some of the African species as currently delimited are very variable, in particular Voacanga bracteata Stapf, supposedly a widespread species with a disjunct distribution in West and Central Africa. A reexamination of herbarium material showed that collections included in this species by Leeuwenberg (1985) represent four different taxa. One of them is endemic to West Africa and represents V. bracteata s.str. Central African specimens previously referred to that species belong in majority to two taxa elevated here at specific rank, V. lanceolata (Stapf) Jongkind (≡ V. bracteata var. lanceolata Stapf) and V. diplochlamys K. Schum.; a complete description of the latter is presented here since the original one (Schumann 1895: 149) is extremely brief. Finally, the type of V. micrantha Pichon, included in V. bracteata by Leeuwenberg (1985), is also distinct from the aforementioned species and probably represents V. psilocalyx Pierre ex Stapf.

Apart from these changes, the new species Voacanga cornuta Jongkind from Gabon is described. The genus now includes 15 species, 10 of which are African. In addition, Cheek et al. (2004: 245) mentioned a “probably new species” of Voacanga (Voacanga sp. 1) from south-west Cameroon, the material of which we have not seen; it apparently differs from most other species of the genus by its connate carpels (also found in V. chalotiana Pierre ex Stapf).

Lectotypus (designated by Leeuwenberg, 1985: 22): Sierra Leone. Southern Prov.: River Bagroo, IV.1861, fl., Mann 858 (K [K000233603]!)

Distribution and ecology. – Sierra Leone, south-eastern Guinea, Liberia, Côte d'Ivoire and Ghana (Fig. 15B), growing in forest from near sea-level to elevations of 610 m.

Notes. – This species is here regarded as a West African endemic; specimens from Central Africa and Nigeria referred to Voacanga bracteata by Leeuwenberg (1985) belong to V. lanceolata (mostly), V. diplochlamys and V. psilocalyx. Differences between the four species are summarised in Table 7. An unusual character of V. bracteata and V. lanceolata, not seen in other species of the genus, is that their corolla lobes change, during flowering, from spreading and cream coloured to reflexed and shiny brown (the corolla seeming still to expand in this process) (Fig. 16C).

Holotypus: Gabon. Woleu-Ntem: Nzec, 9.XI.1933, fl., Le Testu 9385 (BR [BR0000014685156]!; iso-: P [P03859514, P03859516, P03859517] images!, WAG [WAG.1667822]!).

Voacanga cornuta Jongkind resembles V. pachyceras Leeuwenb. by the shape of its fruits and the presence of a short dense indumentum on the lower side of the leaves, but differs by its smaller calyx (10 mm long vs. 15–22 mm long) and shorter corolla lobes (7–8 × 3.5 mm vs. 10–22 × 4–15 mm).

Treelets (?). Twigs cylindrical, glabrous. Leaves opposite, entire; blade 7–18 × 1.5–6 cm, narrowly elliptic or oblong, attenuate at base, acuminate at apex, glabrous above, beneath with many inconspicuous, colourless, tiny, erect hairs; 7–9 pairs of main lateral veins, tertiary venation inconspicuous; petiole 1–2 cm long, with tiny hairs below. Inflorescences terminal and paired, few-flowered, peduncle slender, 3.5–7 cm long, with scattered tiny hairs; bracts up to 7 × 5 mm, glabrous, apex rounded. Flowers 5-merous; pedicel 5–6 mm long, (almost) glabrous. Calyces 10 mm long, colleters scattered inside tube, lobes 5 mm long and wide, acute to rounded at apex. Corollas exceeding calyx, tube c. 21 × 4 mm, lower half conspicuously twisted, gradually narrowed to throat, glabrous outside, inside with a pubescent belt from a few mm above base to insertion of stamens, lobes 7–8 × 3.5 mm, elliptic with rounded apex, glabrous, spreading, in bud forming an almost conical head c. 2 times as long as wide, with a blunt apex. Stamens included but apex close to corolla mouth, glabrous, anthers c. 5.5 mm long, subsessile, sagittate at base, acuminate at apex. Pistils 9 mm long, glabrous; ovary c. 1 mm high, with two free carpels; disk annular; pistil head with a ring connecting it to stamens. Fruits of two separate, narrowly ellipsoid, mericarps; mericarps 3–5 × 0.6–1 cm, acute at apex, many seeded, glabrous. Seeds dark brown, obliquely ellipsoid, 6.5–8 × 3 mm, with a minute tuberculate structure.

Distribution, ecology and phenology. – This species is only known from north-eastern Gabon, but might be expected in adjacent Cameroon and Equatorial Guinea (Fig. 15C); the habitat is not recorded, but presumably, corresponds to lowland evergreen rainforests. Flowers have been collected in November, during the main rainy season, and fruits in March, during the second dry season.

Conservation status. – Voacanga cornuta is known from two collections made in the 1930s in north-eastern Gabon, representing two occurrences, both of which are considered still extant since forest cover is still present in these areas. Based on a 2 × 2 km cell size, its Area of Occupancy [AOO] is estimated as 8 km^2, which falls under the threshold for “Critically Endangered” status under Criterion B2. Its Extent of Occurrence (EOO) cannot be calculated. The two occurrences represent two subpopulations. One occurrence is located within a logging concession, and is threatened by forestry, that induces a decline in its habitat extent and quality. The other occurrence near Bitam is threatened by small scale agriculture, urbanisation and industrial oil palm plantations that are occurring in the area, all of which also inducing a decline in the extent and quality of its habitat. The two occurrences represent two locations (sensu IUCN, 2019) with regard to the most serious plausible threats (small-scale agriculture, urbanisation and industrial oil palm plantations). We infer a past, present and future continuing decline in the habitat extent and quality of this species. Therefore, V. cornuta qualifies for an “Endangered” status [EN B2ab(iii)]. New searches are required in its area of occurrence to better document its distribution and state of conservation. The absence of recent collections would be explained when V. cornuta proves to be an understory species of the closed forests that is not growing in roadsides or near forest edges.

Notes. – This species closely resembles Voacanga pachyceras, which in addition to characters listed in the diagnosis also differs in its distribution, being only known from D.R. Congo with its closest occurrences c. 900 km to the south-east of the range of V. cornuta.

The two collections of Voacanga cornuta were not previously recognised as conspecific. The flowering specimen Le Testu 9385 was cited in the revision of Voacanga (Leeuwenberg, 1985) as V. psilocalyx, which differs from V. cornuta in its glabrous leaves and broader, widely divergent mericarps. The fruiting specimen Le Testu 9040 was cited in the Tabernaemontana revision (Leeuwenberg, 1991) as T. hallei (Boiteau) Leeuwenb. This latter species has a glabrous lower leaf surface, almost sessile inflorescences, and a shorter calyx with free sepals persistent under the fruit; its corolla is also much larger (similar to that of T. glandulosa illustrated in Fig. 14E) and therefore any confusion is unlikely in the flowering stage.

Additional specimen examined. – Gabon. Woleu-Ntem: Bitam, 17.III.1932, fr., Le Testu 9040 (BR, P, WAG).

Lectotypus (designated by Leeuwenberg, 1985): Cameroun. South-West Region: Barombi, 11.III.1889, fl., Preuss 14 (K [K000233602]!).

= Voacanga talbotii Wernham, Cat. Pl. Oban: 63. 1913. Holotypus: Nigeria. Cross River State: Oban, fl., Talbot 1624 (BM [BM000925740]!).

Shrubs or treelets, 2–6 m tall, with abundant white latex. Twigs cylindrical, 1–3.5 mm thick, glabrous, soon covered with dark brown bark. Leaves opposite, entire; blade elliptic to narrowly oblong, 6–22 × 2–9.5 cm, cuneate at base, gradually acuminate at apex, glabrous above, minutely puberulous on midrib and lateral veins below; midrib channelled above, prominent below; secondary veins (8–)10–16 pairs, ascending and almost straight, forming inconspicuous loops close to margin; tertiary veins invisible or very lax; petiole 1–2 cm long, minutely puberulous. Inflorescences terminal, solitary or paired, umbellate to laxly cymose, ± drooping, 5–12 cm long, 4–20-flowered, densely puberulous, with peduncle 4–9 cm long and ramifications up to 2.5 cm long; bracts usually persistent at anthesis, sometimes caducous, ovate to obovate, 6–8 × 3–6 mm, acute to rounded at apex, puberulous outside. Flowers 5-merous; pedicel 4–8 mm long, glabrous to densely puberulous. Calices pale green, 12–19 mm in diam., tube campanulate, 5–6 × 5.5–7 mm, glabrous or puberulous at base outside, provided inside with a discontinuous band of colleters around mid-height, lobes elliptic to obovate, 4–8 × 3–8 mm, rounded at apex, spreading or (usually) reflexed at anthesis, glabrous. Corollas yellow, 7–10 mm in diam., tube 10–12 × 5 mm, slightly longer to slightly shorter than calyx, constricted at throat and a little above mid-height, strongly twisted especially in upper half, glabrous outside, inside with dense band of short appressed pubescence below anthers, lobes obovate, 3.5–7 × 2.5–4 mm, 1.4–1.75 times as long as broad, rounded at apex, patent or reflexed at anthesis, glabrous; anthers included with their tips just reaching corolla throat, attached on corolla tube at around 3/5 of its length from base, subsessile, sagittate, c. 4 mm long, acute at apex, glabrous, with straight tails, coherent and forming a cone around pistil head. Pistils 8–10 mm long; ovary ± hemispherical, c. 1.7 mm long, glabrous, with two free carpels closely appressed against each other; disk annular, c. 1 mm long; style glabrous, c. 6 mm long, narrowly cylindrical, pistil head with saucer-shaped base c. 0.7 × 2 mm and pentagonal domed apex c. 0.7 × 1.2 mm. Fruits (immature) green, consisting of two separate mericarps, these obovate, 3–4 × 2.2–2.5 cm, rounded at apex, glabrous.

Distribution, ecology and phenology. – This species occurs in south-eastern Nigeria, Cameroun, Equatorial Guinea (Rio Muni) and north-eastern Gabon (Fig. 15C) and grows in primary evergreen and secondary regrowth forests, at elevations of 150–760 m. Flowers have been collected mostly from January to March, and in September and October; immature fruits in April, May and October.

Notes. – This species was included by Leeuwenberg (1985) in the synonymy of Voacanga bracteata, and the specimen Brenan 9300 was also cited under the latter by Cable & Cheek (1998). However, the two taxa differ in numerous characters (Table 7) and may be separated even in the vegetative state. The corolla of V. diplochlamys is always reported by collectors to be yellow, and thus does not seem to turn brown after anthesis as in V. bracteata and V. lanceolata. The inflorescence bracts of V. diplochlamys are usually persistent at anthesis, as in V. bracteata, but may occasionally be caducous. Fruits are still imperfectly known, only three immature ones have been seen (Cheek 11571, Esono 17, Etuge & Thomas 27).

Additional specimens examined. – Nigeria. Akwa Ibom State: Eket district, 1912–13, fl., Talbot s.n. (BM [2 sheets]). Cross River State: Old Calabar, s.d., fl., Robb s.n. (BM).

Cameroun. Central Region: Ndanan 1-Ndangan 1, 9.III.2004, fl., imm. fr., Cheek 11571 (BR, K, WAG); c. 5 km S of M'Balmayo, 2.II.1964, fl., W.J.J.O. de Wilde & de Wilde-Duyfjes 1801 (BR, K, P, WAG); Makak, X.1938, fl. & imm. fr., Jacques-Félix 2260 (P); c. 10 km S of M'Balmayo, 9.III.1978, fl., J. Lowe 3565 (K). South Region: 72 km on the road from Ebolowa to Ambam, 16.I.1975, fl., J.J.F.E. de Wilde 7905A (MO, WAG); Akonetye, 17.I.1978, fl., Koufani 60 (P, WAG); près Ngom, 40 km SSE Ebolowa, 2.II.1970, fl., Letouzey 9968 (BR, K, P, WAG); c. 2 km S of Kwambo and 6 km WSW of Bipindi, 19.I.1987, fl., Manning 1461 (MO, WAG); Nkoemvone, 13.II.1963, fl., Raynal 9594 (P); Campo-Ma'an area, Onoyong, 18.III.2001, fl., Tchouto Mbatchou ONOX 85 (WAG); Campo-Ma'an area, Mvini, 19.II.2000, fl., Tchouto Mbatchou 2625 (WAG); Bebai, Campogebiet, 30.X.1908, fl., Tessmann 601 (K); Bipindi, 1911, fl., Zenker 4163 (BM, G, K). South-West Region: Mbalange N.A. Forest Reserve, Southern Bakundu, 16.I.1956, fl., Binuyo & Daramola FHI 35051 (K, P); Banga, S Bakundu F.R., 11.III.1948, fl., Brenan 9300 (K); near Ngombombeng village, N of Nyassosso, 31.IV.1986, imm. fr., Etuge & Thomas 27 (BR, WAG); R.F. d'Ejagham, 29.IX.1984, fl., Onana 85 (P, WAG); R.F. d'Eyumojock, 14.II.1985, fl., Onana 182 (P, WAG); Abonando, 15.III.1902, fl., Rudatis 14 (K); near Kumba, 17.II.1985, fl., Thomas & Nemba 4394 (K, MO, P, WAG).

Equatorial Guinea. Centre Sur: c. 700 m from ECOFAC-Hotel, 1.III.1998, fl., J.J.F.E. de Wilde et.al. 12046 (WAG). Wele-Nzas: Piedra Nzás, 23.V.1998, imm. fr., Esono 17 (BRLU); entre Nsuameyong et inselberg Akuom, 16.I.1998, fl., Obama & Lejoly 413 (BRLU).

Gabon. Woleu-Ntem: Oyem, 21.IX.1933, fl., Le Testu 9399 (BM, P, WAG).

≡ Voacanga bracteata var. lanceolata Stapf, Fl. Trop. Afr. 4(1): 161. 1902.

Lectotypus (designated by Leeuwenberg, 1985: 22): Cameroun. Central Region: Yaoundé, 1896, fl., Zenker 694b (K [K000233768]!; isolecto-: S image!, WU image!).

Distribution and ecology. – A widespread and relatively common species in south-eastern Nigeria, Cameroun, Equatorial Guinea, Gabon, Republic of Congo and Democratic Republic of Congo, in forests up to elevations of 1200 m.

Notes. – This species, originally described as a variety of Voacanga bracteata, is here elevated at species rank; for more information see the Notes section under V. bracteata.