Isolona zenkeri Engl., Notizbl. Bot. Gart. Berlin-Dahlem 2: 301, 1899

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 : 151-153

Isolona zenkeri Engl., Notizbl. Bot. Gart. Berlin-Dahlem 2: 301, 1899

Figs 40 , 41 ; Map 5H

Type.

Cameroon. South Region; Bipindi, Zenker G.A. 1186, 1896: holotype: B[B 10 0154218]; isotypes: BM n.v., G[G00011574]; K[K000199013]; WU[WU0025863] .

Description.

Tree to shrub, 7-15 m tall, d.b.h. up to 15 cm; stilt roots or buttresses absent, trunk not fluted. Indumentum of simple hairs; old leafless branches glabrous, young foliate branches glabrous. Leaves: petiole 2-6 mm long, ca. 2 mm in diameter, glabrous, slightly grooved, blade inserted on top of the petiole; blade 16-23 cm long, 6.5-8.5 cm wide, oblong to oblanceolate, apex abruptly acuminate, acumen 1-2 cm long, base rounded to acute, coriaceous, below glabrous when young and old, above glabrous when young and old, concolorous; midrib raised above, above glabrous when young and old, below glabrous when young and old; secondary veins 11 to 13 pairs, glabrous below; tertiary venation reticulate. Individuals bisexual; inflorescences ramiflorous on young foliate branches, axillary. Flowers with 9 perianth parts in 2 whorls, 1 to 2 per inflorescence; pedicel 3-7 mm long, ca. 1 mm in diameter, glabrous; in fruit 5-15 mm long, 2-3 mm in diameter, glabrous; bracts 2 to 4, all basal, 1 mm long, 1 mm wide; sepals 3, valvate, free, 2-5 mm long, 2-4 mm wide, ovate, apex acute, base truncate, green to brown-red, glabrous outside, glabrous inside, margins flat; petals basally fused, tube 4-7 mm long, inner and outer whorl not differentiated, equal; lobes 15-25 mm long, 3-4 mm wide, lorate (strap-shaped) to oblong, apex acute, light yellow to light green, margins curved inwards, glabrous outside, glabrous inside, erect over receptacle, verrucose when dried; stamens ca. 40, in 3 to 4 rows, ca. 2 mm long, broad; connective discoid, glabrous, cream; staminodes absent; carpels fused into a single structure, ca. 3 mm long, stigma bilobed, slightly capitate, glabrous. Fruit syncarpous, sessile, 30-65 mm long, 15-30 mm in diameter, ellipsoid to globose, apex rounded, glabrous, smooth, faintly ribbed to longitudinally ribbed, green turning yellow when ripe; seeds not counted, 15-20 mm long, 8-10 mm in diameter, ellipsoid; aril absent.

Distribution.

Known from Cameroon to the west of Republic of Congo; in Cameroon known from the South and Littoral regions.

Habitat.

A fairly infrequent species, growing in lowland rain forests. Altitude 0-800 m a.s.l.

Local and common names known in Cameroon.

None recorded.

IUCN conservation status.

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

Uses in Cameroon.

None reported.

Notes.

Isolona zenkeri is characterized by its coriaceous corolla lobes with incurved margins, erect above the receptacle, and verrucose when dried.

Specimens examined.

South Region: Bipinde, 3.26°N, 10.20°E, 16 June 1918, Annet E. 359 (WAG); 12 km from Kribi N of Ebolowa road between Kribi aifield and Kienke R, 2.88°N, 9.983°E, 18 June 1969, Bos J.J. 4866 (BR,K,LM,MO,P,POZG,WAG,YA); 6 km N of km Kribi-Lolodorf, 3.08°N, 10.25°E, 12 March 1970, Bos J.J. 6522 (BR,K,P,WAG,YA); Campo-Ma’an area Bibabimvoto, 2.25°N, 10.36°E, 01 February 2000, Elad M. 1269 (WAG); Campo-Ma’an area Ebianemeyong, 2.46°N, 10.29°E, 24 May 2002, Elad M. 1545 (KRIBI,WAG); 3 km S of Kwambo and 6 km WSW of Bipindi, 3.05°N, 10.36°E, 19 January 1987, Manning D. 1453 (MO); Campo-Ma’an area Bifa, 2.65°N, 10.28°E, 12 October 2001, Tchouto Mbatchou G.P. BIFAX_2 (WAG); Campo-Ma’an area Bibabimvoto, 2.21°N, 10.01°E, 13 May 2000, Tchouto Mbatchou G.P. 2855 (KRIBI,WAG,YA); Campo-Ma’an area Bibabimvoto, 2.25°N, 10.04°E, 24 August 2000, Tchouto Mbatchou G.P. 3009 (KRIBI,WAG,YA); Bipindi , 3.08°N, 10.41°E, 1896, Zenker G.A. 1186 (B,BM,G,K); Bipindi , 3.08°N, 10.42°E, 01 January 1907, Zenker G.A. 3375 (P); Bipindi, 3.08°N, 10.41°E, 01 January 1908, Zenker G.A. 3471 ( US); Bipindi, 3.08°N, 10.41°E, 01 January 1912, Zenker G.A. 4405 (G,K,MO) .

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 40. Isolona zenkeri A flowering branch B flower C fruit. Isolona campanulata D flowering branch; E flower E corolla lobe opened G fruit. Isolona thonneri H flowering branch I flower J fruit A from Le Testu 5117 B from Le Testu 8001 C from Klaine 2675 D-G from Aubreville 6 H, I from Vrydagh 34 J from Lebrun 2032. Drawings by Helene Lamourdedieu, Publications Scientifiques du Museum national d'Histoire naturelle, Paris; modified from Le Thomas (1969 b, pl. 67, p. 359).

Figure 41. Isolona zenkeri A tree in rain forest B detail of funneled trunk C detail of leaves, upper side, note raised midrib D flowers, side view, note erect lobes E flowering and fruiting branch A, B Sosef 2291, Gabon C Sosef 2350, Gabon D, E Sosef 2322, Gabon. Photos Thomas L. P. Couvreur.