Monanthotaxis hexamera P.H.Hoekstra, 2021

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 : 163-165

37. Monanthotaxis hexamera P.H.Hoekstra , sp.nov. — Fig.16 ; Map 23

Monanthotaxis hexamera has the thecae on top of the stamens and a very long filament, a character shared with M. filamentosa . It differs from that species in having short, appressed to ascending white-yellowish hairs on the young branches, while M. filamentosa has long, erect, reddish brown hairs. Furthermore, M. hexamera has 6 stamens and 6 carpels with each 1 ovule, while M. filamentosa has 17–46 stamens and 9–14 carpels with each 7–9 ovules. — Type: R.G. Letouzey 10288 (holo P (P01960096); iso YA0002998), Cameroon,South Region,près Zingui, 20 km WSW d’Ebolowa, Kribi, 5 Apr. 1970.

Etymology. Named hexamera as this species has six petals,six stamens and six carpels.

Liana, to 3 m long; young branches reddish brown, densely covered with appressed to ascending, white-yellowish hairs 0.1–0.2 mm long, becoming glabrous; old branches blackish brown. Leaves: petiole 3–5 mm long, 0.8–1.1 mm diam, slightly grooved, indument as on branches; lamina narrowly oblong-elliptic, 9.5–11.5 by 3.3–4.1 cm, 2.6–3 times longer than wide, chartaceous, not punctate, glaucous below, above glabrous except primary vein densely covered with asending to erect, white-yellowish hairs 0.1–0.2 mm long and becoming glabrous, below sparsely covered with appressed, whitish hairs 0.1–0.2 mm long, base rounded to narrowly subcordate, with slightly thickened black margin, apex acute, secondary veins 11–13 per side, slightly curving, tertiary venation percurrent, hardly visible above. Inflorescences axillary, slightly supra-axillary or terminal, composed of solitary flowers to 4-flowered fascicle-like rhipidia; sympodial rachis 0.5–4 mm long, densely covered with ascending, white-yellowish hairs; flowering pedicels 15–24 mm long, c. 0.4 mm diam, sparsely covered with appressed, white-yellowish hairs 0.1–0.2 mm long; lower bract ovate, 0.6–0.9 by 0.3–0.4 mm, indument as on pedicel; upper bract in the lower half of the pedicel, ovate, 0.5–0.9 by 0.4–0.6 mm, indument as on pedicel; flower buds globose to slightly ovoid. Flowers bisexual; sepals connate at the base, ovate to depressed ovate, 0.8–1 by 1–1.4 mm, apex acute, sparsely covered with yellowish white hairs; receptacle 1.5– 1.8 mm diam, flat; petals white-orange, 6, in two whorls, outer petals ovate, 4.5–8 by 3.7–5.8 mm, outside sparsely covered with yellowish white hairs, inside densely so, but glabrous at the base, inner petals elliptic, c. 5.1 by 2.7–2.9 mm, outside densely covered with yellowish white hairs, base of the inside glabrous; stamens 6, in one whorl, free, linear, c. 2.2 mm long, filaments c. 1.7 mm long, thecae introrse, on top of the filament, connective irregular circular, present on the extrorse side, filament and connective sparsely hairy, staminodes absent; carpels 6, narrowly ellipsoid, 1.6–1.9 by 0.6–0.7 mm, densely covered with whitish hairs, ovule 1, basal, stigma globose, 0.2–0.4 mm diam, glabrous. Monocarps and seeds not seen.

Distribution — Cameroon (South Region).

Habitat & Ecology — In bushy scrub. Flowering: April.

Preliminary IUCN conservation status — Critically endangered ( CR): B2 ab(iii). AOO: 4 km 2. This species is only known from the type collection, which was collected more than 45 years ago outside a protected area .

Figures

Fig. 16 Monanthotaxis hexamera P.H.Hoekstra. a. Flowering branch; b. flower; c. outer petal, inside view; d. outer petal, outside view; e. detail of outer petal, outside; f. inner petal, outside view; g. inner petal, inside view; h. stamen, back view; i. stamen, side view; j. stamen, front view; k. carpel, side view; l. carpel, front view (all: Letouzey 10288, P). — Drawing by H. de Vries.