GABON – Ogooué-Lolo • km 24 Lastoursville – Koulamoutou; 0°58’18.0”S, 12°34’30.4”E; 6 Mar. 2008; fl.; Dessein, Lachenaud, Janssens, Issembé & Nzabi 2392; holotype: BR [BR0000013201128]; isotypes: LBV, WAG.

Figure 1. 

Cladoceras longisepalum. A. Flowering twig. B. Node with stipules. C. Detail of two domatia. D. Flower bud. E. Flower. F. Same in longitudinal section. G. Fruit. A–F from Dessein et al. 2392 (BR); G from Breteler & Lemmens 8307 (BR). Drawing by Hans de Vries.

Figure 2. 

Flowers of Cladoceras longisepalum. Photo by Steven Dessein (from Dessein et al. 2392).

Figure 3. 

Distribution map of Cladoceras longisepalum (triangles), Rutidea viridiflora (solid circles), and Rutidea wieringae (empty circles) with (a) Altos de Nsork NP, (b) Ivindo NP, (c) Lope NP, (d) Waka NP, (e) Birougou NP, and (f) Moukalaba-Doudou NP.

Cladoceras longisepalum differs from C. leonardii (N.Hallé) De Block by its longer corolla tube (10 vs 5.5 mm), corolla lobes externally villose on the part exposed in bud (vs on median axis only) and internally glabrous (vs basally pubescent on median axis), laxer inflorescence with pedicels 1–3(–5) mm long (vs flowers and fruits sessile) and subulate calyx lobes (2.5–)3.5–7.0 mm long (vs lanceolate, 1.7–2.5 mm long).

Woody liana (shrubby when juvenile) up to 10(–30) m high. Branchlets opposite, patent, cylindrical, ca 1.5 mm thick, hirsute with long straight patent to slightly retrorse rufous to whitish hairs 1.5–3.0 mm long. Stipules interpetiolar, 7–12.5 × 3–5 mm, mitriform, shortly sheathing at base for ca 1 mm, acuminate at apex for 2.5–3.5 mm, shiny and thickened in their central part, sparsely hirsute at base and glabrous elsewhere, persistent. Leaves opposite; petiole 0.3–0.7 cm long, hirsute like the branchlets; leaf blade elliptic to ovate, 7–14 × 3.3–7.0 cm, rounded to subcordate and often slightly unequal at base, acuminate at apex, thinly papyraceous, bullate above in life, hirsute on both sides, drying olive green to olive brown; midrib and secondary veins bullate above, the latter 6–11 pairs, strongly curved and ascending, arching 1.5–3.0 mm before the leaf margin; tertiary veins scalariform, lax but prominent on the lower surface, 3–6 mm apart; domatia present as conspicuous hairy tufts in the main vein axils. Inflorescences terminal, cymose, hemispherical, 3.3–4.0 × 6–8 cm, densely hirsute; bracts linear, 6–13 × 0.4–0.7 mm, entire or shortly dentate, hirsute, persistent. Flowers 5-merous; pedicel 1–3(–5) mm long, slender, hirsute. Ovary ca 1 mm long, hirsute, with 2 placentas bearing 3–4 ovules each. Disk cylindrical, ca 0.3 mm long, glabrous. Calyx tube very short, ca 0.5 mm long, hirsute outside, glabrous inside, lobes subulate, (2.5–)3.5–7.0 mm long, hirsute on both sides. Corolla tube pale pink, 10 × 0.7 mm, almost cylindrical, villose outside with ± retrorse hairs, glabrous inside, lobes pale green outside and greenish white inside, elliptic, 5 × 2.3–2.7 cm, rounded at apex, outside villose with patent hairs on the part exposed in bud, glabrous on the part covered in bud, entirely glabrous inside; flower bud claviform with elliptic head, rounded at apex. Stamens spreading, not reflexed, glabrous, filaments ca 1 mm long, anthers completely exserted, pinkish white, linear, 3.5–4.0 × 0.4 mm. Style white, ca 15 mm long (including stigma), ca 6 mm long exserted, sparsely villose in the median 1/4^th, otherwise glabrous, stigma narrowly spindle-shaped, 3.5–4.0 mm long. Fruits white to greenish-white (mature?), globose, 5.0–7.5 mm in diameter when dry, hirsute, with persistent calyx. Seeds 2 per fruit, hemispherical, 4.5 mm in diameter, shiny, smooth, with a deep circular ventral excavation; testa cells with wavy margins.

Cladoceras longisepalum occurs sporadically in central and north-western Gabon, and adjacent south-eastern Equatorial Guinea, and grows in evergreen forest on drained soils, usually in degraded areas (gaps, clearings, roadsides), ca 50–720 m in elevation. The species is evidently uncommon: although it is easily recognisable in the vegetative state, the second author only found it twice during his numerous botanical inventories in Gabon.

The specific epithet, longisepalum, refers to the long calyx lobes which are the longest recorded in the genus.

This species is known from six specimens collected between 1986 and 2020, which represent six occurrences, all of them presumably still extant, and six subpopulations. The extent of occurrence (EOO) is estimated to be 35,331 km², above the threshold for Vulnerable status under subcriterion B1, and its area of occupancy to be 24 km², within the limit for Endangered status under subcriterion B2. The only occurrence in Equatorial Guinea, which coordinates are approximative, is located near the town of Nsork, on the limit of Altos de Nsork National Park; whether it falls outside or just inside the protected area is unclear, but due to the proximity of the town, a decline in habitat extent and quality is expected. Of the five occurrences in Gabon, one (east of Ndjolé) is situated very close to a national road, and potentially at risk from a projected renovation of the road. The remaining four are in former (one) or current (three) logging concessions; whether this represents a threat to the species is unclear, since it seems to tolerate well the level of disturbance induced by selective logging. In view of the above, a decline in habitat extent and quality, number of locations, number of individuals, and AOO is projected. The six occurrences represent six locations in the sense of IUCN with regards to the main threat (roads), and the species qualifies for VU B2ab(ii,iii,iv,v).

The earliest collection of Cladoceras longisepalum, Breteler & Lemmens 8307, was already identified by Degreef (2006: 96) as representing a new taxon related to C. leonardii (then Tarenna leonardii N.Hallé), which he did not describe in the absence of flowers. The new species indeed closely resembles C. leonardii in most of its characters, especially the scandent habit, very long and narrow bracts, and hirsute indumentum covering most of its organs (including both sides of the leaves) but differs by the size and indumentum of the corolla, the development of the pedicels, and the usually longer calyx lobes (Table 1) – which are the longest recorded in the genus, hence the specific name. Although Degreef (2006) mentions calyx lobes up to 3.5 mm long in C. leonardii, this appears to be an error (possibly a slip for 2.5 mm, which is the maximum size we have observed for this species). The two species are apparently inseparable in the vegetative state but have widely separate ranges and different habitats (Table 1).

Several collections from Liberia, first referred to as Rutidea sp. A (Hepper 1963: 146), then as Tarenna sp. (Bridson 1978: 277) or Tarenna sp. A (Hawthorne and Jongkind 2006: 602) are very close to C. longisepalum. Their leaves, inflorescences and calyces are apparently identical, but differences have been noted in the number of ovules (one per locule, as far as seen) and indumentum of the stipules (pubescent externally near the margins). Considering these differences, their widely separate range, and the incomplete state of the Liberian material – with calyces/young fruits only, but no corollas – they might conceivably represent another new taxon, and flowering material would be required to elucidate their status. The concerned specimens are Baldwin 9509 (K) from Sanniquellie [“Sanokwele”]; Whyte s.n. (K) from Sinoe Basin; Yallah 133 (K) from Mt Nimba; and Jongkind & Kpadeyeah 14834 (BR) from Grand Gedeh, 6°10.3’N, 8°37.7’W. Degreef (2006) did not discuss these specimens and apparently did not see them, probably because the material then available was on loan at the time of his work.

EQUATORIAL GUINEA – Rio Muni • Masaha (Nsork); 22 Aug. 2001; imm. fr.; Esono et al. 285; BRLU [BRLU0041452].

GABON – Estuaire • 12 km N of road Libreville-Kango, former concession SOGACEL; c. 0°17’N, 10°05’E; 2 Oct. 1986; fr.; Breteler & Lemmens 8307; BR [BR0000016641556], LBV [LBV0002505], WAG [WAG.1173258]. – Moyen-Ogooué • Route Ndjolé - Alembé entre Camp 5 et Nzamata (au nord de la route); 0°07’07”S, 10°49’32”E; 7 Nov. 2020; st.; Lachenaud et al. 3294; BR [BR0000020471613], BRLU [BRLU0040045], LBV, MO. – Ngounié • Evouta village, nord-est du village, nord du Parc National de Waka; 4 Jul. 2006; fr.; Mayombo et al. 1640; LBV • c. 45 km ESE Ikobey; 1°09.92’S, 11°19.68’E; 4 Apr. 2004; fl. buds; Wieringa et al. 5257; LBV [LBV0035427], WAG [WAG.1206427, WAG.1206428].

GABON – Ogooué-Ivindo • Lope Reserve, SEGC Eaux et Forêts Transect, c. 200 m; 2 Jul. 1993; fl., fr.; White 902; holotype: WAG [WAG.1457883]; isotypes: LBV, MO n.v.

Figure 4. 

Rutidea viridiflora. A. Flowering twig. B. Flowers. C. Mature fruits. D. Leaf from below. Photos by Nicolas Texier (A, B, D, from Texier 1259) and Patricia Barberá (C, from Barberá 3450).

Rutidea viridiflora resembles R. hispida Hiern but differs in its inflorescence with fewer flowers (< 30 vs often > 60) and by its greenish corolla (not white) with a shorter tube (8–11 vs 12–18 mm long).

Slender liana up to 3 m high. Branchlets with fulvous setose hairs up to 3 mm long. Stipules interpetiolar, 5–15 × 1.5–4.0 mm, triangular at base and narrowing to a subulate acumen, entire, pilose. Leaves opposite; petiole 4–16 mm long, indumentum like branchlets; blade elliptic to ovate-elliptic, (4.2–)5–15 × (1.9–)2.5–6.0 cm, rounded to narrowly cordate at base, acuminate at apex, papyraceous and distinctly bullate in life, pilose on both sides but especially on the larger veins below, ciliate on the margin; (5–)7–12 pairs of conspicuous secondary veins nearly reaching the leaf margin, without hairy tufts in the axils, often with a few shorter and less conspicuous intersecondary veins in between; tertiary veins conspicuous, subparallel, 0.5–3.0 mm apart. Inflorescence with < 30 flowers, terminal, up to 8.5 cm long, trichotomous, usually with one pair of lateral branches more or less perpendicular to the main axis, densely hirsute, flowers crowded at the end of the branches, bracts and bracteoles linear-lanceolate, hirsute on both sides, bracts 8–10 × 1.0–1.5 mm, bracteoles 5–6 × 0.6 mm, much longer than calyx. Flowers 5-merous, almost sessile. Ovary < 1 mm long, almost glabrous. Calyx densely appressed hairy outside, lobes triangular, ca 1 × 0.8 mm. Corolla greenish, tube 8–11 mm long, 1–2 mm wide at apex, almost cylindrical but slightly widening at the throat, hirsute outside, inside with a few scattered hairs in the lower half, lobes ovate, 3 × 1.5–2.0 mm, apex acute, hirsute outside, glabrous inside. Stamens spreading, not reflexed, glabrous; filaments very short; anthers almost completely exserted, oblong, 2–3 mm long, attached near the base, shortly apiculate. Style greenish white, glabrous, ca 17 mm long (stigma included), 4–5 mm exserted, stigma fusiform. Fruit globose, 6.0–6.5 mm in diameter when dry, green turning orange, glabrous, sessile, with persistent calyx hidden in a dense tuft of hairs, including a single pyrene, seed ruminate.

Only known from Gabon (but to be expected in the Republic of Congo), relatively widespread in the south and centre of the country, occurring in Moyen-Ogooué, Ngounié, Nyanga, Ogooué-Ivindo, and Ogooué-Lolo provinces; in the understorey of closed evergreen forest, secondary forest and in forest edges, on drained soils or along streams, from 70 to 730 m elevation.

The specific epithet, viridiflora, refers to the flowers that are almost completely green (except for the anthers), whereas most species of Rutidea have white corollas.

This species is known from 11 specimens collected between 1907 and 2023 (6 of them in the last 10 years), representing 11 occurrences and 10 subpopulations. On recent satellite images none of the vegetation where they came from seem to be destroyed so far, apart from the location of the old specimen from “Lastoursville” (Le Testu 8156) that did most likely disappear under the expanding town. Its extent of occurrence (EOO) is estimated to be 50,675 km², far above the threshold for Vulnerable status under criterion B1. Based on a 2 × 2 km cell size, the area of occupancy (AOO) of this species is estimated to be 44 km², below the upper threshold for Endangered under criterion B2. The species is found in two protected areas, Ivindo National Park and Lopé National Park, and may be expected in Moukalaba-Doudou National Park since it has been collected close to its limits. Because of its small size and inconspicuous flowers, it can be easily overlooked and is likely to be undercollected. It grows often in transition zones where forest changes in more open vegetation and it is even found once on a rocky island in a stream (Texier 1259), so it is clear that it could profit from a certain amount of disturbance. With its small size, it might be able to react relatively quickly to changes in its environment. However, at the same time it is clear that it is not common. Huge oil palm plantations, comparable to the one near Mouila, close to where Barberá 3450 was collected, that stretches for about 100 km, might be too much disturbance for this species. The 2 occurrences from Mabounié (Stévart 4186, 4483), potentially at risk from a mining project, are seen as one location. With ≤ 10 locations, of which some are threatened, the species is assessed as VU B2ab(ii,iii).

Bridson (1978) cited Le Testu 8156, the only specimen of this species in 1978, under R. hispida but mentioned that the inflorescence was smaller and with fewer flowers.

GABON – Moyen-Ogooué • Mabounié, between the Ngounié and the camp; 5 May 2012; fl. bud; Stévart & Azizet Issembé 4186; BRLU, LBV, MO [MO-2971350] • Mabounié, along the Ngounié, Camp Somima; 10 May 2012; fr.; Stévart et al. 4483; BRLU, LBV, MO, P [P00855052]. – Ngounié • Concession OLAM, Lot 3, village Moutassou; 6 May 2023; fr.; Barberá et al. 3450; MO. – Nyanga • Concession EBDG au sud-est de Pégnoundou; 16 Oct. 2021; fl. bud; Lachenaud et al. 3623; BRLU, LBV, MO • Doussala–Murindi; 15 Feb. 2023; fr.; Mbading Mbading et al. 872; BRLU, MO. – Ogooué-Ivindo • CFAD Rougier Ivindo, Ouest du Parc National de l’Ivindo, 330 m; 16 Mar. 2009; fr.; Dauby et al. 1744; BR [BR0000005691654], LBV, MO • Ivindo National Park; 0°06’31”S, 12°29’13”E; 730 m; 9 Apr. 2017; fl., fr.; Texier et al. 1259; BRLU [BRLU0015236], LBV, MO, P [P01193703] • Lope Reserve, SEGC; 13 Jul. 1971; fl. buds; White 581; LBV, MO. – Ogooué-Lolo • CFAD EGG Pana Ouest, secteur nord, 7 km ouest de Pana; 3 Mar. 2022; Klein 1011; MO • SIAEFG logging concession, 30 km north of Pana, Monts Birougou; 599 m; 10 Dec. 2017; fr.; Texier et al. 1582; LBV, MO • Lastoursville; 15 Jul. 1930; fl.; Le Testu 8156; BM [BM014608045].

GABON – Ngounié • Fougamou, 17 km on forestry road following Bendolo river; 1°15.0’S, 10°29.5’E; 200 m; 30 Oct. 1994; fl.; Wieringa, van Nek, Hedin & Moussavou 2993; holotype: LBV; isotype: WAG [WAG.1458297].

Figure 5. 

Rutidea wieringae. A. Flowering twig. B. Node with stipules. C. Detail of lower leaf surface. D. Flower bud. E. 5-merous flower and bracteoles. F. 4-merous flower and one bracteole. G. Fruit. A–E from Le Testu 1825 (P), F from Le Testu 1221 (P), G from Florence 1569 (P). Drawing by Olivier Lachenaud.

Differs from R. lujae De Wild. by the fulvous (vs yellowish) indumentum of the inflorescences, corolla glabrous or sparsely hairy externally (vs densely hairy) and usually more numerous secondary leaf veins (7–10 vs 5–7 pairs); and from R. ferruginea Hiern by the bracteoles not exceeding the calyx (vs long exceeding it) and the upper leaf surface glabrous between the veins (vs sparsely scabrid-hairy).

Liana, ca 1 m high. Branchlets densely pubescent, with straight fulvous appressed to half-erect hairs 0.3–1.0 mm long, intermixed with shorter uncinate hairs. Stipules interpetiolar, 7–11 × 2.5–5.0 mm, triangular at base and narrowing to a subulate acumen, entire, pubescent like branchlets. Leaves opposite; petiole 3–16 mm long, pubescent like branchlets; blade elliptic to obovate, (5–)7.5–21 × (2.7–)3.7–10 cm, obtuse to rounded at base, shortly acuminate at apex, papyraceous, glabrous above except the midrib (and sometimes the secondary veins) with short appressed hairs, pubescent on the main veins below (and very sparsely between them) with indumentum similar to branchlets, drying olive green to olive brown; 7–12 pairs of secondary veins irregularly connecting near the margin; tertiary veins laxly reticulate, quaternary veins densely reticulate but hardly distinct; domatia present as hairy tufts in the main vein axils. Inflorescence terminal, pyramidal, 1.5–9.0 cm long, with 1–4 pairs of main lateral branches, the basal ones often themselves branched, ramifications bearing flowers crowded at their end; bracts deeply 2–3-fid, or entire and lanceolate, 2.5–5.0 × 0.5–1.0 mm, pubescent with fulvous appressed hairs outside; bracteoles elliptic to lanceolate, 1.0–1.5 × 0.25–0.5 mm, at most equalling calyx, entire or shortly dentate towards their base, pubescent like the bracts outside. Flowers 5- or more rarely 4-merous, sessile. Ovary hemispherical, ca 0.5 mm long, densely pubescent. Calyx tube ca 0.5 mm long, lobes broadly triangular, ca 0.5 mm, densely villose outside, glabrous inside. Corolla white or cream-white, tube 3.0–4.5 mm long, 0.5–1.0 mm wide, almost cylindrical, glabrous or sparsely hirsute outside, villose inside in the upper third, lobes ovate, 1.5–2.5 × 1.0–1.3 mm, acuminate to obtuse at apex, glabrous or very sparsely hirsute outside, glabrous inside; flower bud acute to acuminate at apex. Stamens spreading, not reflexed, glabrous; filaments ca 0.25 mm long; anthers fully exserted, white, narrowly ovate, ca 1 mm long, attached near the base, shortly apiculate. Style greenish white, glabrous or sparsely villose in median third, 6.5–8.5 mm long (including the stigma), 1.5–2.2 mm exserted, stigma fusiform. Fruit globose to depressed, 4.5–5.0 × 4.5–7.0 mm when dry, green turning orange, glabrous, sessile, with persistent calyx, including a single pyrene, seed ruminate.

Endemic to Gabon, where uncommon and sparsely distributed in Nyanga, Ngounié, and Ogooué-Ivindo provinces; in the understorey of evergreen forest, both along rivers and on drained soils, including degraded areas along roads, 100–500 m in elevation.

The new species is named after Dr Jan Wieringa, collector of the type specimen and of many other interesting African plants.

This species is known from 9 specimens collected between 1907 and 2022, representing 6 occurrences and 5 subpopulations. Its extent of occurrence (EOO) is estimated to be 31,400 km², above the threshold for Vulnerable status under subcriterion B1, and its area of occupancy (AOO) to be 24 km², within the limit for Endangered status under subcriterion B2. One of the occurrences is in a protected area, Ivindo National Park. Another, around Tchibanga, is seriously threatened by urban expansion and shifting agriculture, if not already extirpated. Two occurrences near Mourindi are potentially at risk from shifting agriculture. The remaining two occurrences are in different logging concessions, but do not seem particularly at risk, the species being somewhat heliophilous and appearing to tolerate well the level of disturbance induced by selective logging. In view of the above, a past, present, and future decline in EOO, AOO, habitat extent and quality, number of subpopulations, and number of individuals is inferred. The six occurrences represent five locations with regards to the main threat (shifting agriculture), and the species qualifies for EN B2ab(i,ii,iii,iv,v). Considering the generally low collection density in most of its range, the species is likely to be more widespread, in which case this assessment may have to be revised in the future.

The earliest collections of this species (Le Testu 1221 & 1825) were cited as R. aff. lujae by Pellegrin (1938: 26) who noted their less pubescent corollas. Bridson (1978: 268) also listed them as R. sp. aff. lujae, noting they showed intermediate characters between R. lujae and R. ferruginea, and might represent a new species. The examination of additional material confirms this hypothesis. The three species appear to have separate ranges; differences between them, and also with the related R. gracilis Bridson, are summarised in Table 2. All four species share sessile flowers and fruits, a short corolla tube, and densely pubescent stems.

Flower characters are somewhat variable in R. wieringae. Of the three flowering specimens, Le Testu 1825 has 5-merous flowers with a short corolla tube (3.0–3.5 mm long) and a glabrous style; Le Testu 1221 has 4-merous flowers with a longer corolla tube (4.5 mm long) and a pubescent style; Wieringa et al. 2993 also has a pubescent style but its corolla is similar to Le Testu 1825. The occurrence of 4- and 5-merous flowers in the same Rutidea species is exceptional, since Bridson (1978) even separated two subgenera based on this character; but the collections are otherwise so similar that their conspecificity makes little doubt. Indeed, both Pellegrin (1938) and Bridson (1978) regarded Le Testu 1825 and Le Testu 1221 as representing the same taxon.

The type specimen is described as a shrub, which is presumably an error, since other collections are recorded as lianas, and all Rutidea species are normally scandent.

GABON – Ogooué-Ivindo • Makokou, vers le plateau d’Ipassa; 30 Jun. 1970; fallen fr.; Farron 7578; P [P04019141] • Station d’Ipassa, 10 km S de Makokou; 22 Jul. 1978; fr.; Florence 1569; P. – Nyanga • Concession AEH, 29–30 km à vol d’oiseau au NE de Mayumba; 29 Nov. 2022; fl. buds; Lachenaud & Nguimbit 4060; BR, BRLU, LBV, MO • Dabilila; 12 Nov. 1907; fl.; Le Testu 1221; BM [BM014619466], P [P04019136, P04019139] • Tchibanga; 31 Oct. 1914; fl.; Le Testu 1825; BM [BM014619467], BR [BR0000024875509], P [P04019137, P04019138, P04019140, P04019142] • Monts Doudou, brigade de la Moukalaba à Mourindi; 2°34’S, 10°44’E; 100 m; 19 Mar. 2000; fr.; Sosef et al. 846; LBV, P, WAG [WAG.1325923] • ibid.; 5 Apr. 2000; fr.; Sosef et al. 1102; LBV, WAG • Monts Doudou, à 2 km au Nord de Mourindi; 2°33’S, 10°44’E; 120 m; 18 Apr. 2000; fr.; Sosef et al. 1330; LBV [LBV0036618].