Monanthotaxis discolor (Diels) Verdc.

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 : 147-149

22. Monanthotaxis discolor (Diels) Verdc. — Map 15

Monanthotaxis discolor ( Diels) Verdc. (1971b) 25. — Popowia discolor Diels in Mildbr. (1932) 398. — Lectotype (designated here): H.­J.E. Schlieben 36 (lecto B ( B100153024 ); isolecto B100153025 , B100153026 , BM000553831 , BR0000008804983 , BR0000008805317 , G00308307 , M0107932 , MA384769 , P00362608 ,S), Tanzania, Iringa, Stromgebiet des oberen Ruhudje , Landschaft Lupembe , nördlich des Flusses , Jan. 1931.

Shrub, scandent shrub or liana, to 4 m long; young branches densely covered with ascending to erect, reddish brown hairs 0.2–0.3 mm long, becoming glabrous; old branches grey-black to blackish. Leaves: petiole 3–8 mm long, 0.9–1.6 mm diam, grooved, densely covered with ascending to erect, reddish brown hairs; lamina oblong-ovate, oblong-elliptic to oblong-obovate, 4.8–12.8 by 2.5–5.4 cm, 1.7–2.6 times longer than wide, chartaceous, not punctate, glaucous below, above sparsely covered with ascending, whitish hairs 0.2–0.4 mm long, primary vein more densely covered with yellowish hairs, below sparsely covered with ascending to erect, white hairs 0.4–0.6 mm long, primary vein covered with yellowish hairs, base truncate to subcordate, glands hardly visible, apex acute, secondary veins 8–12 per side, from base straight, halfway curving upwards, tertiary venation percurrent below, distinctly reticulate and raised above. Inflorescences extra-axillary, leaf-opposed or terminal, composed of solitary flowers to 4-flowered rhipidia; sympodial rachis 1.5–2.5 mm long, densely covered with ascending to erect hairs; pedicels 8–24 mm long, 0.4–0.5 mm diam, fruiting pedicels 23–34 mm long, 0.8–1.6 mm diam, densely covered with ascending to erect hairs 0.2–0.3 mm long; lower bracts ovate, 0.5–0.8 by 0.4–0.5 mm, indument as on sympodial rachis; upper bract in the lower half of the pedicel or absent, broadly ovate, c. 0.5 by 0.5 mm, indument as on pedicels; flower buds globose. Flowers bisexual; sepals free, depressed ovate, 1.2–1.5 by 1.5–1.7 mm, apex obtuse, densely covered with hairs, persistent in fruit; receptacle 1.5–2 mm diam, flat; petals colour in vivo unknown, 6, in two whorls, outer petals ovate to broadly ovate, 3.6–3.7 by 2.1–3.5 mm, outside and apical part and margins of the inside densely covered with ascending, yellowish hairs, inner petals elliptic, c. 2.9 by 1.4 mm, outside and apical part of the inside covered with short hairs; stamens 8–12, in one whorl, free, linear-oblong, c. 1.4 mm long, filaments c. 0.5 mm long, thecae latrorse, connective truncate, prolonged outward, not hiding thecae, glabrous, staminodes absent; carpels 8–9(–14), subcylindric to narrowly ellipsoid, c. 1.5 by 0.4 mm, densely hairy, ovules 2, lateral, stigma subglobose, c. 0.2 mm long, glabrous. Monocarps up to 14, colour in vivo unknown, narrowly ellipsoid, 15–24 by 5 –6 mm, constricted between the seeds, slightly verrucose, sparsely covered with ascending, short hairs, apex apiculate, apiculum 1–1.5 mm long, stipes 4–8 mm long. Seeds 1 or 2, ellipsoid, 7–8.5 by 5–6 mm, ochre-brown, apex rounded, raphe visible.

Distribution — Tanzania (Iringa, Mbeya).

Habitat & Ecology — In montane forest. Altitude: 1440– 2050 m. Flowering: January, October; fruiting: March, May, September.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 20 471 km 2, AOO: 24 km 2. This species is known from 4 localities of which 2 fall inside nature reserves. The other localities are under high threat of clearance of natural vegetation for tobacco and tea plantations.

Notes — 1. Monanthotaxis discolor can be recognised in East Africa by the raised and reticulate venation on the upper side of the leaves and the dense indument of ascending to erect, reddish brown hairs on the young branches and lower side of the leaves. Some specimens of M. ochroleuca can show this combination of vegetative characters, but that species has very different flowers, which are axillary and not extra-axillary as in M. discolor .

2. G. S. Bidgood 542 is exceptional, it is slightly more densely hairy than the type specimen and with up to 14 monocarps, while in the flowering specimens only 8 or 9 carpels were counted .

Figures

Map 15 Distribution of Monanthotaxis discolor Diels (●, O means uncertain det) and M. discrepantinervia Verdc. (■).