Osodendron leptophyllum (Harms) 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

3. Osodendron leptophyllum (Harms) E.J.M. Koenen comb. nov.

Fig. 3H-K

Albizia eriorhachis Harms syn. nov., Bot. Jahrb. Syst. 53(3-5): 456. 1915. Type material: Chevalier 7777 (lectotype here designated from amongst the syntypes: P [P00418361] digital image!, isolectotypes: P [P00418360] digital image!, P [P00418362] digital image!, L [L.1992190] digital image!).

Albizia flamignii De Wild., Pl. Bequaert. 3: 49. 1925. Type material: Democratic Republic of Congo, Kitobola, 12 Sept 1910, Flamigni 265 (lectotype designated here: BR! [BR0000016145290], isolectotypes: BR! [BR0000016145283], BR! [BR0000016145306], P [P00418365], digital image!).

Cathormion eriorhachis (Harms) Dandy syn. nov., in F. W. Andrews, Fl. Pl. Anglo-Egypt. Sudan ii. 155. 1952. Type: Based on Albizia eriorhachis Harms.

Arthrosamanea leptophylla var. guineensis G.C.C. Gilbert & Boutique, Bull. Jard. Bot. État Bruxelles 22: 182. 1952. Type material: Democratic Republic of Congo, Yangambi, réserve flore Isalowe, févr. 1940, Louis 16368 (BR!).

Samanea guineensis (G.C.C. Gilbert & Boutique) Brenan & Brummitt, Bol. Soc. Brot. sér. 2, 39: 202. 1965. Type: Based on Arthrosamanea leptophylla var. guineensis G.C.C. Gilbert & Boutique.

Basionym.

Albizia leptophylla Harms, Bot. Jahrb. Syst. 53(3-5): 455. 1915.

Type material.

Democratic Republic of Congo, Kimuenza, 17 km S of Leopoldville, August 1910, Mildbread 3520 (lectotype (designated by Villiers (1989) as holotype, here corrected): HBG [HBG519160] digital image!, isolectotypes: HBG [HBG519161] digital image!, P [P00418364] digital image!).

Description.

Tree or more rarely a shrub, unarmed or with spine-like outgrowths near the base of the bole perhaps associated with adventitious roots (W. Hawthorne, personal communication), to 30 m tall and to 1.25 m in stem diameter, twigs dark with densely scattered small pustular lenticels or sometimes with lighter coloured corky bark. Twigs, stipules, perulate resting buds, all leaf-axes and peduncles covered in dense ferruginous villose indumentum. Foliage consisting of finely divided bipinnate leaves, the leaflets variably ciliate, sometimes with only very few hairs on the margins, the lamina usually glabrous, but sometimes also with a few scattered hairs along the mid-rib on lower surface or rarely pilose or with appressed long hairs on both surfaces especially in lower half, usually distinctly discolourous. The inflorescences consisting of sub-spherical capitula emerging from axillary fascicles of coeval leaves, usually a few below the leaves in the axils of caducous leaves on the same shoots or sometimes also with a few short ramiflorous pseudoracemes, with all leaves caducous, lower down on the branch. Stipules elliptically oblong to asymetrically oblanceolate or falcate, 5-8(-9) × 2-3 mm, more scarcely pubescent or nearly glabrous on adaxial surface, caducous leaving conspicuous scars, perulae deltoid to ovoid, ca. 1.5-5 × 1.5-3.5 mm. Leaves with (10-)12-30(-35) pairs of pinnae, the lower 1-2 pairs of pinnae often shorter with fewer leaflets, petiole pulvinate and flattened on adaxial side at the base, (0.5-)0.8-2.2(-3) cm long, petiolar nectary usually present, cupular and circular, sessile or shortly stipitate and 0.6-1 mm in diameter, in variable position ranging from just above the pulvinule to just below the basal pair of pinnae, rachis canaliculate although often obscured due to dense pubescence, 8-15(-22) cm long, with 1-4(-6) cupular nectaries between the upper pairs of pinnae, these 0.3-0.6 mm in diameter, pinnae pulvinate and with an adaxial ridge, (0.5-)2.5-5(-7.5) cm long, nearly always the abaxial leaflet of the lowermost pair reduced to a paraphyllidium and the adaxial one somewhat smaller than the other leaflets, with elliptical nectaries ca. 0.1-0.25 mm in diameter between the upper 1-3 leaflet pairs, pinnae with (17-)24-35(-42) leaflet pairs, leaflets sessile, pulvinate, asymmetrically oblong to oblanceolate, base oblique to sometimes hastate, apex rounded to acute, (2-)3-6(-9) × (0.3-)0.5-1.2(-2) mm, venation palmately-pinnate brochidodromous, with 2-4 basal veins adaxially next to the mid-rib and 5-8 further secondary veins on each side and reticulate tertiary venation, apart from the mid-rib, all venation often obscure in smaller leaves, otherwise the secondary venation prominent, sometimes only on the lower surface. Capitula 2-4 arranged in fascicles, on peduncles ca. 2.7-4.5 cm, dimorphic with ca. 50-70 peripheral flowers and a single elongated central flower. Bracteoles spatulate, ca. 0.5 mm long, pubescent on outer surface. Flowers white, the peripheral ones on pedicels 0.75-2.5 mm. Calyx slenderly campanulate, green, 5-merous, 2-2.5 mm long, densely puberulous on outer surface, the deltoid lobes ca. 0.25 mm long, corolla 4-4.5 mm long, pubescent on outer surface, the lobes 1.8-2 mm long, stamens 10-14, the filaments white, 11-14 mm long, basally fused into a tube 1.5-2.5 mm long, anthers basifixed, pollen released in 32-celled polyads, pistil on a ca. 0.25-0.75(-1.25) mm long stipe, ovary ca. 1-1.5 mm long, pubescent, style 12-16 mm long, stigma shallowly funnel-shaped. Central flower(s) similar to peripheral flowers, but sessile and longer, calyx ca. 2.5 mm long, corolla ca. 6-6.5 mm long, staminal tube 4-6 mm long, exserted beyond corolla tube. Fruit a dark brown to black indehiscent pod that may tardily disintegrate into 1-multiple-seeded parts, the slightly thickened margins usually straight or also often articulate especially around aborted seeds, the valves papery and thin or with somewhat thickened mesocarp, but not really ligneous, when ripe, swollen over the seeds, when well-fertilised, 12-28(-32)-seeded, (4.5-)10-16(-20) × 0.9-1.3 × 0.4-0.7 cm. Seeds yellowish-brown, 5.5-7.5 × 3-4.5 × 2-3 mm with hard testa and a darker closed pleurogram of 4.5-5.5 × 1.2-1.5 mm.

Distribution.

Lower Guinea and Congolia in Cameroon, Central African Republic, Gabon, Republic of the Congo, Democratic Republic of Congo, Angola (Fig. 3G ).

Ecology.

Forest edges and gallery forest.

Representative specimens examined.

Cameroon: J. Mildbread 8584 (K) ; Democratic Republic of Congo: Luidi , Thysville, Lusolo, 16 October 1959, P. Compere 610 (BR), Isangi, 21 February 1950, Callens 2363 (BR), Petite vallées d’affluente de la Belanzovi, près son confluent avec la Lubimbe, 26 January 1949, A. Michelson 877 (BR, K) .

Notes.

Osodendron leptophylla is highly variable in number of pinnae per leaf, number and size of leaflets and density and length of the indumentum. No consistent correlations between any of these variations have been found suggesting that the material referred to two heterotypic synonyms is best included under O. leptophyllum . The first of these is Albizia eriorhachis , described by Harms in the same publication as A. leptophylla . Specimens from Cameroon, Central African Republic and Gabon, identified as Cathormion eriorhachis , appear to be similar to typical O. leptophyllum , but with relatively large leaflets and denser indumentum. However, the material is not distinct enough to merit recognition as a separate species, given the large variation in leaf dimensions and indumentum in O. leptophyllum across its range and is here placed in its synonymy.

The second is Samanea guineensis , which was originally described as a variety of Arthrosamanea leptophylla , based on more numerous pairs of pinnae and leaflets per leaf, but Brenan and Brummitt (1965) found it to be distinctive enough to recognise it at species rank. Apart from the difference in foliage, they noted differences in the indumentum of the calyx and corolla (glabrous to subglabrous, instead of densely puberulent) and a longer exserted staminal tube. I have observed material that fits their observations (e.g. Jean Louis 10051, BR), but in other collections with the leaf type of " Samanea guineensis ", I have observed dense pubescence on the calyx (e.g. Michelson 877, BR) and vice versa specimens with ca. 15 pairs of pinnae and a subglabrous calyx (Letouzey 9816). Villiers (1989) also judged S. guineensis to be conspecific with S. leptophylla , having also seen numerous specimens with intermediate foliage. I follow Villiers (1989) and place this name in the synonymy of O. leptophyllum .

Figures

Figure 3. A-F Osodendron dinklagei: A trunk of adult specimen in terra firme forest B foliage C detail of pinnae D detail of resting bud and petiolar nectary E inflorescence F pods G distribution map of O. dinklagei and O. leptophyllum as per the legend based on data from Gbif. org H-K O. leptophyllum: H trunk I bipinnate leaf J close-up of leaflets K twig and pods. Images: A-D, F William Hawthorne (FHO) E Xander van der Burgt (K) H-J David Harris (E) K Paul Latham H-K from www. africanplants. senckenberg. de.