Homalium erianthum (Tul.) Baill.

Applequist, Wendy L., 2018, A revision of the Malagasy species of Homalium sect. Blackwellia (Salicaceae), Candollea 73 (2), pp. 221-244 : 231-232

6. Homalium erianthum (Tul.) Baill. in Bull. Mens. Soc. Linn. Paris 1: 574. 1886.

≡ Blackwellia eriantha Tul. in Ann. Sci. Nat., Bot. ser. 4, 8: 62. 1857.

Lectotypus (first step designated by SLEUMER, 1973: 257; second step designated here): MADAGASCAR. Prov. Antsiranana: Nossi-bé , bords de la riv. de Djabal, II.1849, fl., Boivin 2125 ( P [ P00624053 ]!; isolectotype: BM, G [ G00018409 ] image seen, L [ L0010916 ] image seen, P [ P00624052 ]!) . Syntypus: “ Provenit etiam in insula Mauritiana ” [cultivated], Commerson s.n. ( P, not seen) .

Tree to 22 m, 26 cm dbh; bark platanoid; young twigs sparsely short-pubescent to glabrous (moderately pubescent). Leaves elliptical to narrowly (broadly) elliptical (seldom somewhat ovate), 6–13(–15) × 2–6.6 cm; petiole (4–)6–9(–13) mm; base convex (rounded); apex short-acuminate, acute to obtuse, or rounded; margins crenate-serrulate (barely repand), with glands small, in margins of tooth apices; adaxial surface drying darker brown (to near black, paler, or grayish), abaxial surface brown (greenish). Inflorescences paniculate (rarely partly racemose), lateral and pseudoterminal, (3–) 5.5– 15.5 cm, shortpubescent, rarely to villous; flowers pedicellate with pedicels (0.6 –)1 –5(–6) mm; bracts ovate to elliptical, lanceolate or ligulate, 0.8–3.5 mm. Flowers 9–10(–11)-merous; calyx tube long-funnelform with rounded base, moderately to sparsely short-pubescent; sepals ligulate (to narrowly oblong, narrowly deltoid) with acute apex, 1.4–4 mm; petals ligular to narrowly spatulate (narrowly elliptical, oblanceolate) with acute apex, 1.4–4.2 mm; sepals and petals white to pale yellowish green or cream, accrescent, moderately shorter or longer than calyx tube, ascending (seldom partly spreading, then reflexing after anthesis), ciliate mostly towards apex, both surfaces sparsely pubescent (sometimes sparsely villous to pilose adaxially); sepal glands glabrous; filaments 1.5–2.4 mm, moderately pilose to villous; ovary sparsely pilose to villous; styles 5, 1.3–2(–3) mm, basally sparsely pilose to villous.

Vernacular names. – “Hompa” (Service Forestier 12037); “Sarigidroa” (Service Forestier 15786); “Zahamena” (Service Forestier 15958).

Distribution, ecology and conservation status. – Homalium erianthum is primarily native to low-elevation humid forests in the province of Antsiranana, rarely found farther southwest in Mahajanga. It is reported to grow on gneiss and quartzite. The species may be uncommon, as it has not been recollected in some well-botanized areas for several decades. The Area of Occupancy is estimated at 52 km ² and the Extent of Occurrence at c. 74,100 km ². Though most of the habitat is threatened by ongoing anthropogenic damage, the species has been collected in the protected areas of Montagne d’Ambre and Namoroka. More than ten distinct locations are known. Therefore the species’ conservation status is tentatively assessed as “Least Concern” [LC]; however, this may understate its rarity.

Notes. – Among species of Homalium sect. Blackwellia with glabrous glands, H. erianthum is the only species with welldeveloped paniculate inflorescences and has unusually large leaves. SLEUMER (1973) incorrectly cited the material of Boivin 2125 at P as the holotype, which at the time constituted an effective lectotypification. However, since there are actually two duplicates at P, a second-stage lectotypification should select one of them as lectotype. The duplicate chosen has a more complete label and a fragment packet.

Randrianasolo et al. 519 has paniculate inflorescences but leaves that, though possibly immature, are crowded and quite small, resembling those of H. axillare ; it is possibly a hybrid between H. erianthum and H. axillare . Service Forestier 9384 has unusually small leaves and short sepals and petals that are subequal but barely and weakly ciliate, and glabrous. It is suggested that this may represent a hybrid involving H. erianthum and an unknown second parent, possibly from sect. Odontolobus rather than sect. Blackwellia proper.

Additional material examined. – Madagascar. Prov. Antsiranana: Daraina , forêt de Bekaraoka , aux abords du village d’Andranotsimaty , 13°11'S 49°42'E, 130 m, 7.XI.2001, fl., Gautier & Ravelonarivo 4095 ( MO, P) ; Ins. Sakatia prope Nosi-be , II.1880, fl., Hildebrandt 3361 ( P) ; ibid loco, II.1880, fr., Hildebrandt 3361a ( P) ; Vallée de l’Antsahabe , affluent de la Lokoho , 50–300 m, 10–11.III.1949, fl. & fr., Humbert 23351 ( MO, P [2 sheets]); Montagne d’Ambre ( S de Diego ), III.1962, fl., Keraudren 1659 ( P) ; Riv. Ankarakely, Nossibe , XII.1912, fl., Perrier de la Bâthie 6206 [?] ( P) ; Fkt. Manakana, forêt d’Ambondrobe , 13°42'46"S 50°05'25"W, 18.V.2004, fl., Rabehevitra et al. 1062 ( MO, P) ; Plateau de Beankany, Ambanja , 12.XII.1963, fl., Rakotozafy 335 ( P) ; Daraina, forêt d’Ampondrabe , 12°58.33'S 49°42.25'E, 65 m, 13.IV.2004, fl., Ranirison 651 ( MO, P) ; Ankara JB8 , Diego-Suarez , 10.XI.1954, sterile, Service Forestier 12037 ( P) ; Antanamanino, Vohémar , 18.VI.1956, fr., Service Forestier 15958 ( P) ; Le long de l’Andrafiamena affluent du haut Rodo , 8.II.1966, fl., Service Forestier 24548 ( MO [2 sheets], P [2 sheets]); Prov. de Diego-Suarez , s.d., fl. & fr., Ursch 157 ( P) . Prov. Mahajanga: R.N. 8 , Soalala , 14.V.1951, fl. & fr., Réserves Naturelles 3309 ( P) ; Antanimora , Ambolobozo , Analalava , 20.IV.1956, buds, Service Forestier 15786 ( P) .

Possible hybrid specimens. – MADAGASCAR. Prov. Antsiranana: Imahagaga , Montagne des Français , 12°24'42"S 49°22'22"E, 220 m, 14.II.2005, fl., S . Randrianasolo et al. 519 ( MO); Ankara, Diego-Suarez , 11.III.1954, fl. & fr., Service Forestier 9384 ( P) .