Osodendron altissimum (Hook. f.) E.J.M. Koenen, 2022

Koenen, Erik J. M., 2022, Osodendron gen. nov. (Leguminosae, Caesalpinioideae), a new genus of mimosoid legumes of tropical Africa, PhytoKeys 205, pp. 453-470 : 453

1. Osodendron altissimum (Hook. f.) E.J.M. Koenen comb. nov.

Figs 1A , 2

Pithecellobium altissimum (Hook. f.) Oliv., Fl. Trop. Afr. [Oliver et al.] 2: 364. 1871.

Feuilleea altissima (Hook. f.) Kuntze, Revis. Gen. Pl. 1: 187. 1891.

Pithecellobium stuhlmannii Taub., Pflanzenw. Ost-Afrikas C 193. 1895. Type material: Democratic Republic of Congo, Bataibo bei Duki, 850 m, Stuhlmann 2773 (holotype: B†), neotype here designated: Democratic Republic of Congo, Irumu, Bequaert 4887 (BR!).

Albizia passargei Harms, Bot. Jahrb. 26: 253. 1899. Type material: Cameroon, Ngaoundéré, Passarge 164 (holotype: B†), neotype here designated: Cameroon, Bordure du Meng près des lacs de Boubala, Letouzey 2562 (P [P03502143] digital image!).

Cathormion altissimum (Hook. f.) Hutch. & Dandy, Fl. W. Trop. Afr. [Hutchinson & Dalziel] 1: 364. 1928; Hutchinson & Dandy in Kew Bull. 1928 (10): 401. 1928.

Arthrosamanea altissima (Hook. f.) G.C.C. Gilbert & Boutique, Bull. Jard. Bot. État Bruxelles 22: 182. 1952.

Inga altissima (Hook.f.) Roberty, Bull. Inst. Franç. Afrique Noire, A. 16: 343. 1954.

Basionym.

Albizia altissima Hook. f. Niger Fl. [W. J. Hooker]. 332. 1849.

Type material.

Ghana, Cape Coast, 7/41, T. Vogel 18 (lectotype here designated from amongst the syntypes: K!); Nigeria, Aboh, 8/41, T. Vogel 28 (syntype: K!).

Description.

Tree or rarely shrub, unarmed or sometimes with blunt spine-like projections on young twigs (W. Hawthorne, personal communication), 5-35 m tall, stem to 40 cm in diameter. Branches covered with many minute round lenticels 0.1-0.2 mm, twigs, stipules, bud scales, all leaf axes and peduncles brown pubescent, often densely so. Foliage consisting of bipinnate leaves with opposite to sub-opposite pinnae with closely-spaced, distinctly discolourous leaflets, slightly wider in the middle with the apical pair distinctly distally projected, in the basal pair often one or both leaflets reduced to paraphyllidia. The inflorescences consisting of sub-spherical capitula emerging in axillary fascicles, often aggregated into pseudoracemes emerging from the perulate resting buds, with the leaves not fully developing and caducous. Stipules deltoid to linear, 2-8 × 1.0-1.8 mm, caducous, perulae deltoid, 2-4 × 1.8-3 mm. Leaves with (3-)5-7(-8) pairs of pinnae, apical pairs usually slightly longer and the basal pair sometimes much shorter with fewer leaflets, petiole 1.3-2.5 cm, pulvinate, adaxially shallowly canaliculate and often laterally and abaxially grooved, with a circular to elliptic sessile cupular nectary ca. 0.8-2.1 mm in diameter located ca. mid-petiole, rachis (1.8-)4.5-11(-14.5) cm, adaxially shallowly canaliculate and often laterally and abaxially grooved, with 2-5 circular to elliptic sessile cupular nectaries between or just below the distal pairs of pinnae ca. 0.5 mm in diameter, pinna-rachises (2.4-)3.5-8(-10.2) cm, proximally pulvinate, laterally compressed, with elliptic to circular sessile cupular nectaries of 0.2-0.8 × 0.2-0.5 mm between the upper 1-4(-15) leaflet pairs, pinnae with (7-)13-20(-25) leaflet pairs, very often the abaxial leaflet of the lowermost pair reduced to a paraphyllidium, leaflets sessile, pulvinate, inequilaterally hastate or weakly sigmoid, with acute or sometimes obtuse apex or (in subsp. Osodendron altissimum busiraensis ) weakly rhombic with oblique base and mostly obtuse apex or sometimes apiculate, (4-)7-14(-18) × (1.5-)3-4 mm, asymmetrically palmately-pinnate secondary venation with 7-10 veins starting from leaflet base next to the mid-rib and (7-)15-22 major and intercalary secondary veins laterally from the mid-rib, brochidodromous to craspedodromous, distinctly prominent on both surfaces when dry (or obscure on adaxial surface in subsp. Osodendron altissimum busiraensis ), tertiary venation finely reticulate, hardly visible on adaxial surface. Capitula ca. 35-50-flowered, on peduncles 1.8-3.2 cm, dimorphic with 3-9 central flowers with broader base and longer staminal tubes, bracts lanceolate to lanceolate-spatulate, ca. 0.9-1.2 × 0.1-0.2 mm, ciliate in upper half, caducous. Peripheral flowers slenderly campanulate with pale green or greenish-white calyx and corolla, subsessile to shortly pedicellate, pedicel to ca. 0.5 mm, sparsely pubescent. Calyx 5-merous, 2-3.2 mm long, the deltoid lobes ca. 0.5 × 0.5 mm, ciliate at the apex and often also a few scattered short hairs on the outer surface of calyx tube and lobes, otherwise glabrous, corolla 5-merous, 5-7.5 mm long, glabrous, androecium of ca. 20-25 stamens, filaments white, ca. 12-17 mm long, fused into a tube at the base for ca. 2-3 mm, anthers yellow, basifixed, pollen aggregated into 32-celled flattened polyads. Pistil ca. 13-18 mm long, the ovary ca. 3 mm with a few scattered hairs on distal half and the funnel-shaped stigma extending ca. 1 mm beyond the anthers. Central flowers similar, but sessile, broadly campanulate and staminal tube ca. 5.5-8.5 mm long (i.e. the stamens are approximately the same length, but the fused tube is longer than in peripheral flowers), the tube exserted beyond the corolla. Fruit a spirally-curved, twisted or coiled lomentiform pod, usually articulate between the seeds, breaking up tardily after abscission in water or on the forest floor, often with arenchymous swollen mesocarp for flotation, (10-)18-29(-30) × (0.8-)1.1-1.7 × 0.2-0.6 cm, (3-)9-20(-23) seeded. Seeds plano-compressed, nearly round or slightly elliptic, ca. 5-7.5 × 4-6 × 1.5-2 mm, chestnut brown with a small 2.1-3.2 × 1-1.5 mm elliptic to obovate or oblong open pleurogram.

Notes.

A specimen seen at Kew, of Espírito Santo 1858, collected in Guinée-Bissau, is doubtfully placed in this species. This specimen is highly unusual in the number of pairs of pinnae (13) and leaflet pairs (14-35) and the leaflets appear relatively small and elongate (even though they appear not fully expanded), while having the typical asymmetrical hastate shape. Furthermore, the fruit is not clearly articulate and also differs in being only somewhat curved rather than twisted or coiled. Brenan and Brummitt (1965) also cited this material as being unusual and speculated that it may be a distinct taxon. I do not share this opinion as I do not think it is sufficiently morphologically distinct. It is perhaps more likely of hybrid origin with O. dinklagei , which occurs sympatrically, as the other parent. However, this unusual specimen resembles O. altissimum much more closely than O. dinklagei and the number of pinnae and leaflets and dimensions of the leaflets clearly distinguish it from that species.

The holotype of Pithecellobium stuhlmannii was destroyed at B and no surviving isotypes are known. According to the Flora of East Tropical Africa ( Brenan 1959), the original material was collected in the Democratic Republic of Congo, west of Lake Albert. The specimen of Bequaert 4887 from BR is from the same region, includes leaves, flowers and immature fruit and matches the description in the protologue and is here selected as the neotype of P. stuhlmannii .

The holotype of Albizia passargei was also destroyed at B, but Villiers (1989) placed the name in synonymy with C. altissimum , based on the description in the protologue. A specimen of Letouzey 2562 from P, comprising leaves and flowers, is here chosen as the neotype as it was collected in N Cameroon (ca. 150 km SW of the type locality) and matches the description in the protologue.

Figures

Figure 1. Confusing pods of Cathormion s. l. A pods of Osodendron altissimum that are very similar to B pods of the Australian species Albizia moniliformis (DC.) F. Muell. (syn. Cathormion umbellatum subsp. moniliforme (DC.) Brummit) C pods of Osodendron dinklagei and D pods of Osodendron leptophyllum that were likened to those of E Samanea (S. saman (Jacq.) Merr. is pictured here) and / or Cathormion F pods of Hydrochorea obliquifoliolata (De Wild.) E. J. M. Koenen (syn. Cathormion obliquifoliolatum) that are superficially similar to those of O. leptophyllum in particular; hence, this species having also been classified in a broadly circumscribed Cathormion in the past, but note that the pods become disarticulated while still on the tree rather than tardily as in Osodendron and Albizia moniliformis G and H pods of the closest relative of Osodendron, the Neotropical genus Robrichia (R. schomburgkii is pictured here). Images: A Jos Stevens, voucher unknown B Russel Cumming, voucher unknown C J. Alves Pereira 2664 (MA) D R. Gutzwiller 1865 (P) E J. F. Maxwell 91 - 300 (L) F B. Descoings 8278 (MPU) G Cristoph Moning, voucher unknown H Jose Benito Quezada Bonilla, J. B. Quezada Bonilla 623 (HULE, MO). A from www. africanplants. senckenberg. de B-H from www. gbif. org B-G distributed under a Creative Commons BY-NC-SA 4.0 Licence H distributed under a Creative Commons BY-NC-SA 3.0 Licence.

Figure 2. Osodendron altissimum A distribution of the two subspecies as per the legend, based on data from Gbif. org with the addition of occurrence records for O. altissimum subsp. busiraensis from specimens at BR B trunk on riverbank C bipinnate leaf D close-up of leaflets E close-up of rachis apex showing nectary F inflorescences G unripe pod H mature pod. Images: B, F, H William Hawthorne (FHO) C-E, G David Harris (E), from www. africanplants. senckenberg. de.