Monanthotaxis dictyoneura (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 : 146-147

20. Monanthotaxis dictyoneura (Diels) Verdc. — Map 14

Monanthotaxis dictyoneura ( Diels) Verdc. (1971b) 25. — Popowia dictyoneura Diels in Mildbr. (1933) 811. — Lectotype (designated by Verdcourt 1971a: 98): H.­J.E. Schlieben 1686 (lecto B100153027 ; isolecto BM000553830 , BR0000008803993 , BR0000008804327 , BR0000008804655 , G00308306 , HBG-502536, LISC000380 , M0107933 , MA384770 , MA384770-2 , P00362611 , S), Tanzania, Morogoro, Ulanga district, Mahenge , Muhulu Mts , SSW von station Mahenge , c. 1200 m, 30 Jan. 1932.

Small tree or scandent shrub, to 8 m tall; young branches blackish, sparsely covered with appressed hairs 0.1–0.2 mm long, becoming glabrous; old branches blackish. Leaves: petiole 3–4 mm long, 0.8–1.2 mm diam, grooved, sparsely covered with appressed, yellow hairs c. 0.1 mm long; lamina narrowly obovate, narrowly oblong-elliptic to narrowly ovate, 5.4–12.8(–14.7) by 2.4–4.3(–6.5) cm, 2.3–3.2 times longer than wide, subcoriaceous, not punctate, discolorous, shiny dark green above, glaucous below, above glabrous or primary vein covered with appressed, very short hairs, below glabrous or sparsely covered with appressed, yellowish hairs c. 0.1 mm long, base rounded to subcordate, glands hardly visible, apex acute to acuminate, acumen to 25 mm long, secondary veins 11–15 per side, from base straight, halfway curving upwards, tertiary venation reticulate to slightly percurrent, distinctly raised and reticulate above. Inflorescences extra-axillary, leaf-opposed or terminal, composed of solitary flowers to 4-flowered rhipidia; sympodial rachis 1.3–2.5 mm long, sparsely covered with appressed, yellowish, short hairs; pedicels 7–12 mm long, 0.4–0.6 mm diam, fruiting pedicels c. 16 mm long, c. 1.2 mm diam, indument as on sympodial rachis; lower bracts absent or ovate to orbicular, 0.5–0.8 by c. 0.5 mm, indument as on rachis; upper bract in the lower half of the pedicel or halfway or absent, broadly ovate, c. 0.5 by 0.5 mm, densely covered with appressed, yellowish hairs; flower buds globose. Flowers bisexual; sepals slightly connate at the base, depressed ovate to shallowly triangular, 0.6–1.4 by 2–2.2 mm, apex obtuse to acute, sparsely covered with appressed hairs c. 0.1 mm long, persistent in fruit; receptacle 1.7–3 mm diam, flat; petals colour in vivo unknown, 6, in two whorls, outer petals broadly ovate, 4.5–5.1 by 4.8–5.5 mm, outside and apical part and margins of the inside sparsely covered with appressed hairs c. 0.1 mm long, inner petals elliptic, 4–4.6 by 2.7–2.8 mm, elliptic, outside and inside covered with very short hairs; stamens 9–14, in one whorl or in three groups of 4 –5 opposite the inner petals, free, linear-oblong, 1.4–1.6 mm long, filaments 0.6–0.7 mm long, thecae latrorse to extrorse, connective truncate, prolonged inward and outward, slightly papillate, staminodes absent; carpels 9–14, subcylindric, 1.9–2 by 0.4–0.5 mm, densely hairy, ovules 2, lateral, stigma elongate, 0.7–0.8 mm long, glabrous. Monocarps 2, colour in vivo unknown, narrowly ellipsoid, 15– 21 by 6 –7 mm, slightly constricted between the seeds, slightly verrucose, sparsely covered with appressed hairs c. 0.1 mm long, apex rounded to mucronate, stipes 3.5–5 mm long. Seeds 1 or 2, ellipsoid, c. 8 by 6 mm, ochre-brown.

Distribution — Tanzania (Iringa, Morogoro).

Habitat & Ecology — In montane forest. Altitude: 1200– 1760 m. Flowering: December, January; fruiting: October.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 5 246 km 2, AOO: 24 km 2. This species is known from 3 localities of which one is at the edge of the Udzungwa Mountains National Park. The locations are threatened by forest clearance for agriculture.

Notes — 1. Monanthotaxis dictyoneura can be distinguished from other species in East Africa by the almost glabrous narrowly obovate to narrowly oblong-elliptic leaves with clearly raised reticulate venation on the upper side. The leaves of some specimens of M. orophila can appear similar, but that species has large, leafy bracts, in contrast to the very small or absent bracts in M. dictyoneura .

2. Only a single fruit with two monocarps has been seen.

3. Despite some similarity, C. Frimodt­Moller TZ517 and W.R.Q. Luke 6669 have not been assigned to this species, due to the incompleteness of the material and the larger-sized leaves.

Figures

Map 14 Distribution of Monanthotaxis dictyoneura Diels (■) and M. faulknerae Verdc. (●, O means uncertain det).