Strombosiopsis sereinii Breteler, 2001

Breteler, F. J., 2001, Novitates Gabonenses 40. A new species of Strombosiopsis (Olacaceae) from Gabon, Adansonia (3) 23 (2), pp. 303-306 : 303-306

Strombosiopsis sereinii Breteler , sp. nov.

Strombosiopsis tetrandrae Engl. affinis, sed differt ramunculis teretibus, calyce non lobato, petalis antherisque longe coalescentibus et fructu mesocarpium manifeste evolutum instructo.

TYPUS. — Breteler, Caballé, Issembe, Moussavou, Pascal & Serein 14829, Gabon, Forêt des Abeilles , Makandé (0°41’S, 11°55’E), 28 Jan. 1999, fr. (holo-, WAG; iso-, BR, G, K, LBV, MA, MO, NY, P, PRE).

Tree to c. 20 m tall, trunk to c. 40 cm diam., glabrous throughout; bark ≥ 1 cm thick, fibrous, reddish in section. Branchlets slightly flattened when very young, soon (sub)terete, green. Leaves: petiole subterete, shallowly and often narrowly canaliculate (or groove ± closed) above, (12-)15- 25(-30) mm long, slightly swollen at distal end or not; blade ± soft-leathery, brittle, elliptic to oblong-obovate, 16-30 × 6-12(-15) cm, 2-3 times as long as wide, broadly rounded and/or shortly cuneate at base, obtuse to acutish at apex (mucronate-apiculate when young); midrib and the (8-)9-10(-12) pairs of main lateral nerves ± plane above, prominent beneath, the veins between the lateral nerves plane to very slightly impressed on both sides, ± parallel, 2-4 mm apart, ± indistinct above, ± distinct beneath. Flowers 4-merous, in a subaxillary fascicle of up to ± 35 flowers; bracts minute, triangular-ovate, ± 1 mm long, apex rounded to lobulate; bracteoles much narrower and slightly shorter. Pedicel terete, 3-4 mm long; calyx cupular, ± 1mm long with a thin undulate margin; petals pale-green to cream-coloured, thick, free, sometimes slighly adnate at base, narrowly elliptic,

6 × 1.5-2 mm, apex acute; stamens slightly shorter than petals, anthers (sub)sessile, adnate to petals for

at least 3/4 of their length or even entirely so, apex acute; disc indistinct; pistil ± conical, style obscurely 4-lobed. Mature fruit pale green with paler stripes, ± smooth, globose to slightly obovoid, c. 3 cm diam., stipe 3-5 mm long; calyx rim-like in fruit, strongly widened, leaving free the fruit apex (see Fig. 1J ); exocarp (including the ± fleshy calyx) 2-2.5 mm thick with an inner hard layer of c. 1 mm thick; mesocarp c. 3 mm thick, fleshy; endocarp indistinct. Seed globose, ± 1.5 cm diam., with a thin, brown testa. — Figs. 1 , 2.

HABITAT AND DISTRIBUTION. — Rain forest of

Gabon, alt. up to c. 500 m.

PARATYPES. — GABON: Arends et al. 400, Waka, Nov., fl. ( BR, LBV, WAG) ; Breteler et al. 14829, Forêt des Abeilles , Makandé, Jan., fr. ( BR, G, K, LBV, MA, MO, NY, P, PRE, WAG) , type; Breteler et al. 15540, Monts de Cristal, Assok Rd., Aug., fr. ( WAG) ; Breteler et al. 15642, Oct., fl. ( LBV, WAG) .

This species is named after Jean-Yves SEREIN, co-collector of the type specimen and an excellent tree climber.

The three species of Strombosiopsis may be distinguished as follows:

1. Shrub or treelet up to 3 m tall; leaves (7-)9-15 × 3-5 cm, with 5-7(-8) pairs of main lateral nerves; petiole 0.5-1.6 cm long; fruit up to 2 × 1.5 cm without widened calyx. Liberia............................ S. nana Breteler

1’. Tree to c. 30 m tall, trunk to 100 cm diam., rarely a flowering treelet of c. 4 m; leaves (7-)11-30 × (4-)5- 12(-15) cm, with 6-10(-12) pairs of main lateral nerves; petiole 1-2.6(-3) cm long; fruit 2.5-3.5 × 2-3 cm with a distinctly widened calyx. Nigeria to Uganda and Angola................................................................ 2

2. Branchlets (sub)terete; main lateral nerves (8-)9-10(-12) pairs; calyx entire with an undulate margin, rimlike in fruit; anthers completely adnate to petals or nearly so; fruit with very distinct mesocarp c. 3 mm thick. Gabon.................................................................................................................. S. sereinii Breteler

2’. Branchlets angular or narrowly winged; main lateral nerves 6-8(-11) pairs; calyx distinctly lobed, usually also in fruit; anthers adnate to petals only at base; mesocarp indistinct in fruit. Nigeria to Uganda and Angola.. ........................................................................................................................................ S. tetrandra Engl.

Figures

Fig. 1. — Strombosiopsis sereinii Breteler: A, part of flowering branch; B, petiole; C, leaf apex; D, inflorescence; E, flower bud; F, flower in longitudinal section cut lengthwise; G-H, petal with adnate anther; I, young fruit; J, mature fruit seen from above; K, fruit in transverse section. (A, D-H, Arends et al. 400; B, C, I-K, Breteler et al. 14829). Drawing by H. DE VRIES.

Fig. 2. — Distribution of Strombosiopsis sereinii Breteler.