Uvariastrum zenkeri Engl. & Diels

Tree or shrub to 20 m high, d.b.h. up to 30 cm; old branches spreading, glabrous, bark brown-grey; young branches glabrous to very sparsely pubescent, hairs ca. 0,1 mm long, appressed, light brown soon disappearing; leaf buds elongated, pubescent, hairs ca. 0.2 mm long, appressed, light brown. Petioles 2–3 mm long, 1.5–2 mm in diameter; glabrous, or rarely very sparsely pubescent, hairs tiny, light brown, soon falling off; leaf lamina inserted on top, not grooved adaxially. Leaf lamina (12-)15–22 cm long, 3–5 cm wide, length:width ratio 2–4.7, narrowly elliptic to elliptic or narrowly obovate to obovate, coriaceous, glabrous adaxially, sparsely pubescent, hairs tiny, light brown, becoming quickly glabrous abaxially; lamina dark green adaxially; slightly lighter green abaxially; base rounded to cuneate, apex acuminate, acumen 1–2 cm long; midrib glabrous on both sides; secondary veins 11–17, curving upwards, anastomizing near margins, glabrous, slightly raised adaxially; clearly visible abaxially. Raphidia 1–2 on young and old braches, cauliflorous with numerous flowers. Flowering pedicels 1.3–3 cm long, 1–2 mm wide, glabrous to very sparsely pubescent, hairs ca. 0.1 mm long, appressed, light brown, drying black or brown, brown to dark green in fresh material. Bracts up to 3, basal, up to 5 mm long, 3 mm wide, length:width ratio 1.6, ovate, sparsely pubescent outside, glabrous inside. Flower buds pyramidal, up to 2.5 cm long, up to 1.5 cm in diameter, margins weakly to strongly folded. Sepals 1.5–2.5 cm long, 0.8–1.5 cm wide, length:width ratio 1.2–2, ovate to broadly ovate, base truncate, apex acute, margins clearly recurved, glabrous or sparsely pubescent outside, hairs 0.1–0.2 mm long, appressed, light brown, tomentose light brown inside along the margins, glabrous towards the center; sepals conspicuously black outside, light brown inside but black at the centre on dry material; same color as flowering pedicels on fresh material, spreading horizontally at anthesis. Outer petals 2–3.5 cm long, 0.8–1.5 cm wide, length:width ratio 2–3.5, ovate to narrowly ovate or elliptic to narrowly elliptic, base truncate, apex acute, densely pubescent outside more so along the main vein, hairs ca. 0.1–0.2 mm long, appressed, light brown shiny, pubescent along the margins to glabrous at the center inside, hairs ca. 0.1 mm long, appressed, light brown; petals light brown outside, light brown to black inside in herbarium material, white turning bright yellow to orange in fresh material, light grey when old; spreading horizontally at anthesis. Inner petals 1.5–2.5 cm long, 0.7–1 cm wide, length:width ratio 1.5–3.5, ovate to narrowly ovate, base truncate, apex acute, pubescence same as outer petals, color same as outer petals, connivent to appressed by the margins, the top open. Receptacle pyramidal with a flat apex. Stamens 2–4 mm long, connective discoid, pubescent, ca. 0.2 mm in diameter, red in fresh material. Carpels (1–3-)5–15, 3–5 mm long, ca. 1 mm in diameter, stigma capitate, ca. 0.7 mm in diameter, glabrous or sometimes very sparsely pubescent, drying black; ovules numerous. Fruiting pedicels 1.5–3 cm long, 2–5 mm in diameter, woody, glabrous. Monocarps 2–5, up to 8 cm long, up to 2.5 cm in diameter, oblong to narrowly oblong, straight to slightly bending, apex acute, longitudinally ribbed, main ribs 5–6, sometimes with smaller latitudinal ribs, glabrous to sparsely pubescent, hairs ca. 0.1 mm long, appressed, light brown; stipe 2–5 mm long, ca. 5 mm in diameter; monocarps. Seeds 20–27 per monocarp, 1.5–2 cm long, 1–1.5 cm wide, ellipsoid flat, ca. 5 mm in depth, testa light brown in herbarium material, raphe very slightly raised, hilum 3–4 mm long, 2–3 mm wide, narrowly elliptic.

This species has a strict Central African distribution occurring from extreme east Nigeria and South East Cameron till Democratic Republic of Congo; 0–600 m. Figure 13.

Uvariastrum zenkeri is a species of plant in the Annonaceae family. It is found in Cameroon and Nigeria. It is threatened by habitat loss.

Uvariastrum zenkeri Engl. & Diels est une espèce de plantes de la famille des Annonaceae et du genre Uvariastrum, présente en Afrique tropicale.

Uvariastrum zenkeri là một loài thực vật thuộc họ Annonaceae. Loài này có ở Cameroon và Nigeria. Chúng hiện đang bị đe dọa vì mất môi trường sống.