Homalium retivenium Sleumer

Applequist, Wendy L., 2018, A revision of the Malagasy species of Homalium sect. Blackwellia (Salicaceae), Candollea 73 (2), pp. 221-244 : 240

13. Homalium retivenium Sleumer in Bull. Jard. Bot. Natl. Belg. 43: 264. 1973.

Holotypus: MADAGASCAR. Prov. Toamasina: Env. de Navana ( à l’E de Maroantsetra ), I.1954, fl. & fr., Service Forestier 8884 ( P [ P00375174 ]!; isotype: L [ L0011003 ] image seen, P [ P04734404 , P04734406 ]!, TEF [ TEF000233 ] image seen) .

Tree to 16 m, 12 cm dbh; latex white; young twigs glabrous. Leaves obovate to elliptical, oblanceolate or narrowly elliptical, 2.8–7.5 × 1.3–3.8 cm; petiole 1–3.5 mm; base cuneate to convex; apex rounded-acute to short-acuminate (rounded, cuspidate); margins entire or subentire, usually revolute, with glands absent or inconspicuous; adaxial surface drying grayish (blackish brown), abaxial surface brown to olive. Inflorescences racemose, lateral, often paired, 1.8–6.8(–10) cm, moderately pilose; flowers pedicellate with pedicels 1 – 2.4(– 4.5) mm, apparently early caducous; bracts linear to lanceolate, (0.7–) 1– 1.8 mm. Flowers (7–)8–9-merous; calyx tube short or narrowly funnelform with narrow base, sparsely (to moderately) pilose; sepals linear to narrowly ligulate (narrowly spatulate) with acute apex, 2.5–5.5(–6.4) mm; petals linear to narrowly ligulate with acute apex, 2.5–5.5(–6.8) mm; sepals and petals greenish-white to yellowish, strongly accrescent, much longer than calyx tube, ascending (sometimes becoming spreading, seldom to reflexed), long-ciliate, both surfaces sparsely pilose; sepal glands moderately pilose on apex; filaments 2–3 mm, moderately pilose; ovary sparsely pilose; styles 3–4, (1.6–) 2.5–3.4 mm, basally pilose.

Vernacular names. – “Hazombato à p[etits] f[euilles]” (Service Forestier 15758); “Hazombatofotsy” (Service Forestier 2791, 15694); “Marankoditra” (Réserves Naturelles 6193); “Tsilaitra” (Raharimalala 219).

Distribution, ecology and conservation status. – Homalium retivenium is native to low-elevation and littoral forests in northeastern Madagascar. There are more than five distinct localities, and the species occurs in several protected areas, including Betampona, Masoala, Nosy Mangabe, and Tampolo. Therefore, a preliminary assessment of its conservation status is “Least Concern” [LC].

Notes. – Among eastern species of sect. Blackwellia with racemose inflorescences and pubescent sepal glands, H. retivenium is notable for its pilose inflorescences and flowers and its relatively numerous, long, narrow sepals and petals, much exceeding the calyx tube (which at anthesis is rather short and narrow).

The only specimen included in H. retivenium from the province of Antsiranana, Service Forestier 2791, is morphologically atypical with very long inflorescences and pedicels and unusually broad sepals and petals. Further investigation of this population would be desirable.

Additional material examined. – MADAGASCAR. Prov. Antsiranana: Ampavatonampingotra , Andapa , 12.II.1951, fr., Service Forestier 2791 ( P) . Prov. Toamasina: Maroantsetra , fkt. Ambanizana , 15°37'00"S 49°57'00"E, 10.IV.2002, fl., Antilahimena & Aridy 962 ( MO, P) ; Betampona RNI , fkt. Andratambe , 17°55'S 49°13'E, 250–650 m, I-X.2000, fl., Iambana et al. 268 ( G, MO) ; Forêt d’Ibanda , 2.II.1990, fl., Raharimalala 219 ( P) ; RN I [ Betampona ], Ambodiriana, Tamatave , 12.II.1954, fr., Réserves Naturelles 6193 ( MO, P) ; Masoala Peninsula c. 6 km NNE of Ambanizana along trail from Ambanizana River to summit of Ambohitsitondroina, 24–25.XII.1989, fl., Schatz & Modeste 2910 ( MO, P) ; Nosy Mangabe in the Bay of Antongil , 15°30'S 49°46'E, 0–330 m, 2–19.I.1990, fl., Schatz & Carlson 2926 ( MO, P) ; Masoala Peninsula , along coast at third major river , approx. 6 km S of Ambanizana, 0–10 m, 26.XII.1990, fl., Schatz & Modeste 3092 ( MO, P) ; Tampolo, Fénérive , 14.II.1956, fl. & fr., Service Forestier 15694 ( MO, P [2 sheets]) ; Vohilengo, Fénérive-Est , 20.II.1956, fl. & fr., Service Forestier 15758 ( P) .