Isolona hexaloba (Pierre) Engler, Nat. Pflanzenfam. Nachtr. zu 3(2): 161, 1897

Couvreur, Thomas L. P., Dagallier, Leo-Paul M. J., Crozier, Francoise, Ghogue, Jean-Paul, Hoekstra, Paul H., Kamdem, Narcisse G., Johnson, David M., Murray, Nancy A. & Sonke, Bonaventure, 2022, Flora of Cameroon - Annonaceae Vol 45, PhytoKeys 207, pp. 1-532 : 141-144

Isolona hexaloba (Pierre) Engler, Nat. Pflanzenfam. Nachtr. zu 3(2): 161, 1897

Figs 37 , 38 ; Map 5D

≡ Monodora hexaloba Pierre, Fig. Herb. L. Pierre, del. E. Delpy 5/1896, 1896.

= Isolona bruneelii De Wild., Ann. Mus. Congo Belge, Bot. ser. 5, 3(1): 82, 1909. Type. Democratic Republic of the Congo. Orientale, Dikila, Bruneel A.C.E. s.n., Dec 1906: lectotype, sheet here designated: BR[BR0000008800152]; isotypes: BR[BR0000008799692, BR0000008799364, BR0000008799302]; S[S10-20956].

= Isolona seretii De Wild., Ann. Mus. Congo Belge, Bot. ser. 5, 3[1]: 82, 1909. Type. Democratic Republic of the Congo. Equateur, near Nala, Seret F. 792, Mar 1907: lectotype, sheet here designated: BR[BR0000008800992]; isotype: BR[BR0000008801326].

= Isolona solheidii De Wild., Ann. Mus. Congo Belge, Bot. sér. 5, 3: 83, 1909. Type. Democratic Republic of the Congo. Equateur, surroundings of Yambuya, Solheid A.F. s.n., 1906: lectotype, sheet here designated: BR[BR0000008799395]; isotype: BR[BR0000008799722].

= Isolona seretii var. grandifolia De Wild., Ét. Fl. Bang. Ub.: 313, 1911. Type. Democratic Republic of the Congo. Orientale, Mobwasa, Claessens J. 615, Apr 1910: holotype: BR.

= Isolona pleurocarpa subsp. nigerica Keay, Kew Bull. 7: 157, 1952. Type. Nigeria. Ijebu State, Shasha Forest Reserve, Richards P.W. 3343, 8 Apr 1935: holotype: BM[BM000546386]; isotypes: BR[BR0000014130090]; G[G00011543, G00011544]; MO[MO-2246487]; S[S10-20983].

Type.

Gabon. Estuaire; Environs de Libreville , Klaine T.-J. 360, 17 Feb 1896: lectotype, sheet here designated: P[P00363270]; isotypes: B; K[K00198842]; P[P00363269, P00363268]; WAG[WAG0251603] .

Description.

Tree to shrub, 15-30 m tall, d.b.h. up to 50 cm; stilt roots or buttresses absent, trunk deeply fluted. Indumentum absent; old leafless branches glabrous, young foliate branches glabrous. Leaves: petiole 2-4 mm long, 2-3 mm in diameter, glabrous, grooved, blade inserted on the side of the petiole; blade 10-28 cm long, 3-11 cm wide, ovate to elliptic, apex acuminate, acumen 1-2 cm long, base obtuse to acute, coriaceous, below glabrous when young and old, above glabrous when young and old, concolorous; midrib raised, above glabrous when young and old, below glabrous when young and old; secondary veins 8 to 16 pairs, glabrous below; tertiary venation reticulate. Individuals bisexual; inflorescences ramiflorous on old or young foliate branches, axillary. Flowers with 9 perianth parts in 2 whorls, 1 to 2 per inflorescence; pedicel 7-30 mm long, ca. 1 mm in diameter, glabrous; in fruit 20-29 mm long, 3-5 mm in diameter, glabrous; bracts 3 to 5, several basal and one upper towards the lower half of pedicel, basal bracts ca. 1 mm long, 0.5 mm wide; upper bract 2-5 mm long, ca. 1 mm wide; sepals 3, valvate, free, 1-3 mm long, 2-4 mm wide, elliptic, apex acuminate, base truncate, green, glabrous outside, glabrous inside, margins flat; petals basally fused, tube 4-10 mm long, inner and outer whorl not differentiated, equal; lobes 6-25 mm long, 4-12 mm wide, elliptic to ovate, apex acute to rounded, dark red, margins flat to wavy, glabrous outside, glabrous inside, spreading horizontally; stamens numerous, in 3 to 4 rows, 2 mm long, broad; connective discoid, glabrous, green; staminodes absent; carpels fused into a single structure, ca. 1 mm long, stigma bilobed, slightly capitate, glabrous. Fruit syncarpous, sessile, 30-70 mm long, 25-40 mm in diameter, ovoid, apex rounded, glabrous, smooth, bumpy, irregularly and transversely ribbed, light green to dark purple when ripe; seeds not counted, 8-15 mm long, 4-6 mm in diameter, ellipsoid; aril absent.

Distribution.

A widespread species from Nigeria to the Democratic Republic of Congo and northern Angola (one specimen); in Cameroon known from Adamaoua, East, South, Central, Littoral and South-West, North-West regions.

Habitat.

A relatively rare species in Cameroon; in lowland primary and secondary evergreen forests, but also in semi-deciduous forests, also along rivers. Altitude 0-700 m a.s.l.

Local and common names known in Cameroon.

None recorded.

IUCN conservation status.

Least Concern (LC) ( Cosiaux et al. 2019t).

Uses in Cameroon.

None reported.

Notes.

Isolona hexaloba is distinguished by the short and grooved petiole with the leaf blade inserted on its sides. The corolla lobes are coriaceous and can be quite variable in shape, ranging from elliptic to obovate, with a narrowed base. It is a polymorphic species and has been described under several names, now all reduced to synonymy ( Couvreur 2009). Isolona hexaloba resembles I. cooperi by the shape of the corolla lobes, but is distinguished by the insertion of the leaf blade on the side a short petiole and lacks the strong sweet smell. Isolona hexaloba is also similar to I. pleurocarpa , but the later can be distinguished by its decurrent to narrowly cuneate leaf bases, longer petioles, and papyraceous corolla lobes.

Specimens examined.

Central Region: Tibati près Mbatimbang , 6.14°N, 12.48°E, 04 December 1959, Letouzey R. 2392 (P,YA) . East Region: A 25 km environ à l’ENE de Mikel village situé à 85 km au N de Moloundou sur la route de Yokadouma 2.93°N, 15.33°E, 24 February 1971, Letouzey R. 10419 (P,WAG,YA); A 14 km à l’Ouest de Yenga Port Gentil village situé à 35 km au NNE de Moloundou, 2.35°N, 15.35°E, 21 April 1971, Letouzey R. 10703 (BR,COI,K,P,WAG,YA); A 20 km au Sud de Mboy I (45 km à l'Est de Yokadouma ), 3.38°N, 15.13°E, 16 May 1963, Letouzey R. 5072 (K,P,WAG,YA) . Littoral Region: Douala (route Razel ), 4.05°N, 9.71°E, 01 January 1955, Endengle E. SRFK 2121 (P,YA); Roue forestière SNCB (km 36 vers Ndoksom) environ 25 km Sud Yabassi, 4.31°N, 9.958°E, 11 May 1976, Letouzey R. 14910 (C,K,MO,P,WAG,YA); Tissongo, 3.58°N, 9.9°E, 01 August 1976, McKey D.B. 245 (K) . South Region: ca 15 km east from Lélé village, 2.28°N, 13.32°E, 10 September 2013, Couvreur T.L.P. 495 (WAG,YA); near Bipaga II km 40 road Kribi-Edéa, 3.15°N, 10.01°E, 30 December 1982, de Kruif A.P.M. 998 (MO,WAG,YA); 17 km S of the Lobe river along the road to Campo, 2.81°N, 10.13°E, 18 March 1975, de Wilde J.J.F.E 8088 (BR,K,MO,P,U,WAG,YA); A l’Ouest d’Alati (100 km SE de Djoum), 2.2°N, 13.42°E, 13 January 1973, Letouzey R. 11840 (K,P,YA); 22 km on road Kribi to Campo 12 km past Gross Batanga, 2.76°N, 9.881°E, 24 February 1994, Wieringa J.J. 2327 (MPU,U,WAG); Bipindi, 3.08°N, 10.41°E, 01 November 1901, Zenker G.A. s.n. (P) . South-West Region: Korup National Park , 5.01°N, 8.783°E, 31 October 2005, van der Burgt X.M. 791 (BR,G,K,MO,P,WAG,YA) . West Region: Bali- Ngemba FR, 5.81°N, 10.08°E, 13 April 2002, Onana J.M. 2030 (K,WAG) .

Figures

Map 5. A Isolona congolana B Isolona cooperi C Isolona dewevrei D Isolona hexaloba E Isolona pilosa F Isolona pleurocarpa G Isolona thonneri H Isolona zenkeri I Letestudoxa bella. White borders represent region limits in Cameroon; green patches represent protected areas (see methods and Suppl. material 1: Fig. S 1).

Figure 37. Isolona hexaloba A, B flowering branch C transversal section of flower showing androecium and stigma D flower (bottom view) E stamens inner row (2 top); stamens of inner most row (top) and outermost row (bottom) F carpel and detail of ovules G fruits, the one on the right opened to show seeds H seed (left) and transversal section of seed showing ruminate endosperm (right) A, C-F from Le Testu 5862 B Le Testu 5836 G, H Klaine 360. Drawings by Helene Lamourdedieu, Publications Scientifiques du Museum national d'Histoire naturelle, Paris; modified from Le Thomas (1969 b, pl. 66, p. 357).

Figure 38. Isolona hexaloba A trunk, note deeply furrowed B base of leaf blade, note raise midrib C flower, top view D flower, side view E fruiting branch. Isolona pleurocarpa F trunk G bade of leaf blade, notice decurrent base H flower, top view, fallen on ground I syncarpous fruit; fallen on ground A Sosef 2032, Gabon B-D Couvreur 561, Gabon E Texier 2347, Gabon F-I Couvreur 402, Ngovayang, Cameroon. Photos A-D, F-I Thomas L. P. Couvreur E Nicolas Texier, Tropicos. org, Missouri Botanical Garden.