Monanthotaxis dielsiana (Engl.) P.H.Hoekstra

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 : 147

21. Monanthotaxis dielsiana (Engl.) P.H.Hoekstra — Map 13

Monanthotaxis dielsiana (Engl.) P.H.Hoekstra in Guo et al.(2017) 14. — Unona dielsiana Engl. in Diels (1907) 476. — Oxymitra dielsiana (Engl.) Sprague & Hutch. (1916) 156. — Richella dielsiana (Engl.) R.E.Fr. in Engl. & Harms (1959) 139. — Friesodielsia dielsiana (Engl.) Steenis (1964) 359. — Lectotype (designated here): G.A. Zenker 2473 (lecto B (B100154098); isolecto B100154096,B100154097,B100154099,BM001125043,BR000008801388, COI00071518,E, G00308364;GOET005688,GOET005689,HBG502481, K000198948, KFTA 0001554, KFTA 0001555, L 0182291, M-0240178, P00363342, P00363343, P01988326, S07-13404, WAG0057970, WU 0025876), Cameroon, South Province, Bipinde, Dec. 1901.

Liana; young branches densely covered with appressed, orange-brown hairs c. 0.5 mm long, becoming glabrous; old branches greyish. Leaves: petiole 6–11 mm long, 1.6–2 mm diam, terete, indument as on branches; lamina narrowly oblong-elliptic to oblanceolate, 10.3–21.3 by 3.3–3.8 cm, 3.1–4.8 times longer than wide, membranous to subcoriaceous, not punctate, glaucous below, glabrous above, but primary vein densely covered with appressed yellowish white hairs 0.1– 0.3 mm long, below subglabrous, but primary vein sparsely covered with appressed to erect, whitish hairs, base slightly subcordate, with a thickened, black margin, apex acuminate, acumen 5–25 mm long, secondary veins 7–14 per side, first straight but curving upwards at end, tertiary venation percurrent, not raised above. Inflorescences leaf-opposed, composed of solitary flowers or 2- or 3-flowered fascicles; sympodial rachis c. 8 mm long, rather densely covered with erect, orange-brown hairs 0.2–0.4 mm long; pedicels 15–27 mm long, 1.4–2.1 mm diam, fruiting pedicels to 2.9 mm diam, indument more dense than on sympodial rachis; lower bracts ovate to lanceolate, c. 3.5 by 1–2 mm, indument as on sympodial rachis; upper bract placed halfway or in upper half of pedicel, broadly ovate, c. 4.5 by 4.2 mm, indument as on pedicel; flower buds globose. Flowers bisexual; sepals free, broadly triangular, c. 4 by 4 mm, apex acute, densely covered with appressed yellow-brown hairs; receptacle c. 4.5 mm diam, convex; petals colour in vivo unknown, 6, in two whorls, outer petals ovate, 10–15 by 8–9 mm, outside densely covered with yellow-brown, short hairs, inside glabrous at the base, inner petals broadly ovate, c. 8 by 7.7 mm, outside densely covered with hairs, but less densely so near the margins, inside glabrous; stamens c. 65, in three whorls, free, linear, c. 1.2 mm long, filaments c. 0.1 mm long, thecae latrorse, connective truncate, circular seen from above, hiding thecae, c. 0.2 mm thick above the thecae, glabrous, staminodes absent; carpels c. 41, ellipsoid, c. 1.7 by 0.7 mm, densely hairy, ovules 1 or 2, basal, stigma subsessile, globose, c. 0.1 mm diam, glabrous. Monocarps 1– 6, brown when young, narrowly ellipsoid to cylindric, c. 45 by 10–12 mm, tuberculate-rugulose, densely covered with erect, yellow-brown hairs c. 0.7 mm long, apex rounded, stipes c. 3 mm long. Seeds 1 or 2, cylindric-ellipsoid, c. 15 by 9 mm.

Distribution — Cameroon (Central Region, South Region).

Habitat & Ecology — In primary rain forest.Altitude: c. 200 m. Flowering: December; fruiting: March.

Preliminary IUCN conservation status — Critically endangered (CR): B2ab(iii). AOO: 8 km 2. This species is only known from 2 collections from southern Cameroon of more than 50 years ago, from unprotected areas.

Note — The flowers and leaves of M. dielsiana are very similar to M. enghiana and M. glaucifolia , but M. dielsiana differs in the dense indument of appressed, yellow to orange-brown hairs on the young branches, while M. enghiana has longer and erect dark brown hairs and M. glaucifolia has a dense indument of appressed, pale brown hairs. Additionally, M. dielsiana has a much lower number of stamens compared to the other 2 species and the seeds are cylindric-ellipsoid instead of ellipsoid.

Figures

Map 13 Distribution of Monanthotaxis diclina (Sprague) Verdc. (■) and M. dielsiana Engl. (●, O means uncertain dets).