Isolona congolana (De Wild. & T. Durand) Engl. & Diels, Monogr. Afrik. Pflanzen.-Fam. 6: 84, 1901

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 : 133-136

Isolona congolana (De Wild. & T. Durand) Engl. & Diels, Monogr. Afrik. Pflanzen.-Fam. 6: 84, 1901

Figs 33 , 34 ; Map 5A

≡ Monodora congolana De Wild. & T. Durand, Bull. Soc. Roy. Bot. Belgique 38: 13, 1899.

= Isolona maitlandii Keay, Kew Bull. 7(2): 155, 1952. Type. Cameroon. North-West Province, Ngong, Maitland T.D. 1555, Jun 1931: holotype: K[K000105576]; isotypes: BM, FHO.

Type.

Democratic Republic of the Congo. Equateur; Lukandu, Dewèvre A.P. 1103, 19 Nov 1896: lectotype, sheet here designated: BR[BR0000006248932]; isotypes: BR[BR0000006248857, BR0000006249588, BR0000006249250] .

Description.

Tree, 10-30 m tall, d.b.h. 5-45 cm; stilt roots or buttresses absent. Indumentum of simple hairs; old leafless branches glabrous, young foliate branches densely pubescent. Leaves: petiole 4-7 mm long, 2-3 mm in diameter, densely pubescent, grooved, blade inserted on top of the petiole; blade 13-19 cm long, 4-5 cm wide, narrowly ovate to narrowly elliptic or oblong, apex acuminate, acumen 0.5-1 cm long, base cuneate to rounded, subcoriaceous, below sparsely pubescent when young, glabrous when old, above sparsely pubescent when young, glabrous when old, concolorous; midrib raised, above sparsely pubescent when young, glabrous when old, below sparsely pubescent when young, glabrous when old; secondary veins 11 to 14 pairs, sparsely pubescent to glabrous below; tertiary venation reticulate. Individuals bisexual; inflorescences ramiflorous on old leafless or young foliate branches, axillary. Flowers with 9 perianth parts in 2 whorls, 1 to 3 per inflorescence; pedicel 10-23 mm long, 1 mm in diameter, sparsely pubescent to glabrous; in fruit 2-5 mm long, 2-3 mm in diameter, glabrous; bracts 3 to 4, several basal and one upper towards the lower half of pedicel, basal bracts 1 mm long, 1 mm wide; upper bracts 1 mm long, 1 mm wide; sepals 3, valvate, free, 3 mm long, 2 mm wide, ovate, apex acute, base truncate, green, pubescent outside, glabrous inside, margins flat; petals basally fused, tube 4-10 mm long, inner and outer whorl not differentiated, equal; lobes 9-20 mm long, 3-7 mm wide, elliptic to ovate, apex rounded, green turning red, margins wavy, glabrous outside, densely pubescent inside, spreading horizontally; stamens numerous, in 3 to 4 rows, 2 mm long, broad; connective discoid, densely pubescent, cream; staminodes absent; carpels fused into a single structure, 2 mm long, stigma bilobed, slightly capitate, densely pubescent. Fruit syncarpous, sessile, 60-80 mm long, 40-50 mm in diameter, ellipsoid, apex rounded, glabrous, smooth to verrucose, irregularly ribbed, green when ripe; seeds not counted, 15-25 mm long, 10-15 mm in diameter, ellipsoid; aril absent.

Distribution.

A central African species, with a disjunct distribution between the Cameroon Volcanic Line in Cameroon, and Eastern Democratic Republic of Congo, one collection from Central African Republic; in Cameroon known from the Littoral, North-West and South-West regions.

Habitat.

A common species when present, mainly in montane or premontane rain forests, along rivers and bush land. Altitude 800-1700 m a.s.l.

Local and common names known in Cameroon.

Ndin (Westphal 10012).

IUCN conservation status.

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

Uses in Cameroon.

food: fruit for condiments, spices, flavourings (Westphal 10012).

Notes.

This the only species of Isolona growing above 1000 m in Cameroon. Isolona congolana is characterized by the densely pubescent inner part of the corolla tube and a glabrous outer part of the tube, a unique feature in this genus ( I. pilosa is pubescent on both sides of the corolla). The leaves are also characteristic being narrowly ovate to narrowly elliptic or oblong, giving a unique aspect to the foliage.

Specimens examined.

Littoral Region: Manengouba Mt 4 km WNW Of Nkongsamba, 4.98°N, 9.900°E, 04 April 1972, Leeuwenberg A.J.M. 9550 (B,BR,C,GC,H,K,LD,M,MO,P,WAG,YA). North-West Region : Kagwene, 6.12°N, 9.734°E, 20 May 2009, Ashworth J. 196 (K,YA); Bamenda Distr Ngong, 6.58°N, 10.43°E, 01 June 1931, Maitland T.D. 1555 (BM,K); Bamenda Wae, 6°N, 10.41°E, 01 April 1931, Maitland T.D. 1596 (K). South-West Region : Nyasoso, 4.86°N, 9.7°E, 04 June 1996, Cable S. 2843 (K,MO,WAG,YA); 2 km north of Nyasoso towards Mpako, 4.84°N, 9.679°E, 04 April 2016, Couvreur T.L.P. 1054 (WAG,YA); Nyasoso, 4.83°N, 9.683°E, 19 March 1996, Etuge M. 1794 (K,WAG); White trail (above Kupe village ) towards Madam 4.78°N, 9.716°E, 28 May 1996, Etuge M. 2000 (BR,K,MO,P,WAG,YA); Lake Edip , 4.95°N, 9.65°E, 21 November 1998, Etuge M. 4488 (K,WAG,YA); Etube Tape from Nyasoso, 4.83°N, 9.683°E, 06 February 1995, Lane P. 532 (K,YA); Bu 4.15°N, 9.233°E, 6 June 1898, Lehmbach H. 224 (B). West Region: Bali Ngemba Forest Reserve, 5.82°N, 10.08°E, 13 April 2004, Etuge M. 5431 (K,WAG,YA); Along the road 6 km W of Dschang on road to Fongo Ndeng, 5.45°N, 9.95°E, 15 May 1978, Westphal E. 10012 (P,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 33. Isolona campanulata A flower, side view B flower, top view. Isolona congolana C flowering branch D base of leaf blade, top view E flower, top view F flower, bottom view G syncarpous fruit A, B no voucher, Bayang Mbo, Cameroon C-G Couvreur 1054, Mt Cameroon. Photos A, B Sonneck C-G Thomas L. P. Couvreur.

Figure 34. Isolona congolana A flowering branch B Flowers C young flower bud D flower E transversal section of flower showing receptacle, stigma and stamens F stamen G fruit A, C-F Leeuwenberg 9550 B Wesphal 10012 G Richardson 234. Drawings by Hans de Vries (Couvreur 2009, fig. 19, p. 39).