Homalium intercedens Sleumer

4. Homalium intercedens Sleumer in Bull. Jard. Bot. Belg. 43: 300. 1973.

Holotypus: MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: plateau calcaire de l’Ankarana, à l’E d’Ambondromifehy, 8.III.1951, fr., Service Forestier 3047 (P [P00375092]!; iso-: P [P04677610, P04677611]!).

Tree to 25 m tall, 30 cm dbh; bark gray-white, exfoliating, platanoid; twigs dark brown, glabrous, leafing internodes ca. 0.7–1.3 mm diam.; stipules free, caducous. Leaves lanceolate, 3.4–6.7 × 1.2–2.4 cm; base convex; apex acuminate; margin serrulate with round to elongated glands in tooth apices; secondary veins 10–12(–14) per side; both surfaces glabrous, drying dark brown with paler veins on adaxial surface, lighter to greenish on abaxial surface; petiole glabrous, 7–16 mm. Inflorescences racemose, axillary, 2.1–2.8 cm; rachis glabrous; bracts and bracteoles glabrous, ca. 1.5–2.5 mm; flowers borne singly. Flowers (5–)6-merous, yellowish-green; sepals narrowly oblanceolate to nearly ligulate, 6–8 mm in fruit, adaxial surface with appressed pubescence on calyx cup and sparsely pubescent on sepal bases, adaxial surface glabrous; sepal glands glabrous; petals deltoid-ovate, 2.5–3 mm in fruit, abaxial surface short-pubescent, adaxial surface glabrous; filaments glabrous, ca. 2 mm; anthers not seen; styles ca. 1.5–1.8 mm.

Distribution, ecology and conservation status. – Homalium intercedens is known only from Ankarana in the DIANA region in the extreme north of Madagascar. It is reported on limestone and at a relatively low altitude. It is known from only one subpopulation (or perhaps two subpopulations close together) and rarely collected. Ankarana has been visited by many collectors over the years. TROPICOS (2020) has databased over 2100 historical and recent specimens from the area so the small number of collections is likely to indicate that the taxon is either narrowly endemic or uncommon within its range. However, the population is in a protected area that is known for inaccessible terrain, so it is at little risk of loss due to human activity. Therefore, its conservation status is tentatively assessed as “Least Concern” [LC].

Notes. – Homalium intercedens is easily distinguished from other species of sect. Nisa by its free stipules (caducous, but leaving two stipule scars rather than a single fused scar) and small lanceolate leaves with serrulate margins.

Additional material examined. – MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: Ambilobe, Mahamasina, RS d’Ankarana, chemin du canyon forestier, 12°55'22"S 049°06'27"E, 130 m, 16.I.2003, fr., Bardot-Vaucoulon et al. 1207 (P).