Monanthotaxis congoensis Baill.

Hoekstra, P. H., Wieringa, J. J., Maas, P. J. M. & Chatrou, L. W., 2021, Revision of the African species of Monanthotaxis (Annonaceae), Blumea 66 (2), pp. 107-221 : 142-144

16. Monanthotaxis congoensis Baill. — Fig. 10a–g ; Map 12

Monanthotaxis congoensis Baill. (1890) 878. — Lectotype (designated by Le Thomas 1969: 258): F.R. Thollon 813 (lecto consisting of 3 sheets: P00362762 , P00362763 , P00362766 ; isolecto K000198992 , MA630761 , MA698356 , WAG0003586 , WAG0003587 ), Gabon, Congo, Ogooué, July 1887.

Small understory tree, shrub or liana, 1.5–5 m long; young branches densely covered with appressed, pale brown hairs 0.7–1.2 mm long, becoming glabrous; old branches dark brown to blackish. Leaves: petiole 3–8 mm long, c. 1 mm diam, grooved, densely covered with hairs; lamina narrowly obovate to narrowly oblong-elliptic, 7.5–25 by 1.9–6 cm, (2.3–)3.1–4.4 times longer than wide, chartaceous, sometimes slightly punctate, glaucous below, young leaves above sparsely covered with appressed white hairs 2–3 mm long, becoming glabrous, below densely covered with appressed, white hairs 1–2.5 mm long below, less densely so in older leaves, base rounded to slightly cordate, sometimes broadly cuneate, sometimes with small, thickened black margin, apex acute to acuminate, acumen to 15 mm long, secondary veins 9–16 per side, oblique, curving upwards, tertiary venation percurrent to somewhat reticulate, slightly raised above, below only visible in older leaves. Inflorescences axillary or terminal, 6–13 cm long, 4–10-flowered raceme-like rhipidia; sympodial rachis sparsely to densely covered with white, short hairs, internodes up to 25 mm long, 1 (or 2) flowers in the axil of each lower bract; flowering and fruiting pedicels up to 12 mm long and 0.5 mm diam, indument as on rachis; lower bracts lanceolate, 2–3 by c. 0.5 mm, indument as on rachis, upper bract absent; flower buds deltoid-ovoid. Flowers bisexual; sepals free or slightly connate, broadly ovate to triangular, 0.5–2.5 by 0.5–1.5 mm, densely covered with white hairs, apex acute; receptacle c. 2 mm diam, convex; petals greenish to yellow, inside paler, 6, in one whorl, ovate to lanceolate, 3–4 by 1–2 mm, outside densely covered with hairs, inside covered with hairs <0.1 mm long; stamens 6, in one whorl, opposite the petals, free, obconical, c. 0.7 mm long, filaments c. 0.4 mm long, thecae introrse, connective truncate, apex c. 0.8 mm wide, not hiding the thecae, glabrous, staminodes 6, alternating with the stamens, c. 0.6 mm long, filaments c. 0.3 mm long, thecae introrse, staminodes with 2 dorsal theca-like appendages c. 0.4 mm wide, carpels 15–21, ellipsoid, c. 0.7 by 0.3 mm, densely covered with reddish brown hairs, ovule 1, basal, stigma bifurcate, c. 0.2 mm long, glabrous. Monocarps up to 4, dull orange to red, ellipsoid to subglobose, 12–15 by 9–10 mm, densely covered with pale brown hairs c. 0.5 mm long, apex rounded; stipes 2–3 mm long. Seeds 1, ellipsoid to globose, 8–9 by 7–8 mm, ochre-brown, both ends rounded, raphe a longitudinal furrow.

Distribution — Cameroon (Littoral, South-West Region), Gabon (Estuaire, Moyen-Ogooué, Ngounié, Ogooué-Ivindo, Ogooué-Lolo).

Habitat & Ecology — In primary periodically inundated forest, gallery forest, forest edges, primary rain forest and old secondary forest on rocky soil. Altitude: 90– 626 m. Flowering: March to May, November, December; fruiting: all year round.

Preliminary IUCN conservation status — Least concern (LC). EOO: 168 369 km 2, AOO: 88 km 2. This species is known from many locations, including a few national parks.

Notes — 1. Monanthotaxis congoensis can easily be distinguished from all species of Monanthotaxis by its raceme-like inflorescences.

2. The sterile specimen K. Schmitt 66 from the Cross River National Park in Nigeria has also a dense indument of appressed hairs on the lower side of the leaves, but has shorter and wider leaves than typical specimens of M. congoensis . Fertile material is needed to verify if M. congoensis also occurs in Nigeria.

3. Le Thomas (1969) cited F. R. Thollon 813 ( P) as holotype. Likely, P was the only herbarium holding this gathering at the time of description and the P set hence could be considered as holotype, since all traced sheets in other herbariums arrived after 1890. But, when doubted, Le Thomas’s remark should be regarded as a lectotypification, where the sheets in P become the lectotype. The set of sheets in P mentions the set consists of 4 sheets, but only 3 were traced by us .

Figures

Map 12 Distribution of Monanthotaxis congoensis Baill. (●) and M. couvreurii P.H.Hoekstra (■).

Fig. 10 a–g. Monanthotaxis congoensis Baill. a. Flowering branch; b. petal inner and outside view; c. flower with three petals removed; d. stamen front view and seen from above; e. staminodes; f. carpel and longitudinal section of carpel; g. longitudinal section of seed. — h–o. Monanthotaxis montana (Engl. & Diels) P.H.Hoekstra. h. Flowering branch; i. outer petal; j. inner petal; k. flower with petals removed; l. stamen, front and side view; m. carpel and longitudinal section of carpel; n. fruiting branch; o. transverse section of seed (a–g: Thollon 813; h–m: Le Testu 4364; n–o: Tisserant 1362). — Modified from Le Thomas (1969) plates 42 and 45.