Homalium nobile Baill.

Wendy L. Applequist, 2016, Revision of the Malagasy species of Homalium sect. Eumyriantheia Warb. (Salicaceae), Candollea 71 (1), pp. 33-60 : 47-48

8. Homalium nobile Baill. in Bull. Mens. Soc. Linn. Paris 1: 575. 1889.

Lectotypus (designated by Sleumer, 1973: 325): Madagascar. Prov. Toamasina: Ampasimbola, 21.VIII.1881, fl., Humblot 33 ( P [ P04734254 ]!; isolecto-: W ). Syntypus: Madagascar. Prov. Toamasina: Antsianaka, 5.III.1883, fl., Humblot 659 ( K [ K000231464 , K000231466 , K000231467 ] images seen, P [ P04734255 , P04734274 ]!, TAN [ TAN000594 ] image seen, W).

Tree to 16 m tall, 20 cm dbh; large twigs dark brown to greenish- or grayish-brown; young twigs dark brown to grayish- or red-brown, sparsely to moderately short-pubescent when young; stipules narrowly lanceolate to linear, 2- 3.3 mm, short-pubescent. Leaves alternate (rarely subopposite); petiole 7-23 mm, sparsely short-pubescent (sometimes becoming glabrous); blade elliptical to obovate (broadly obovate), (5.5-)6.5-18 × (3-) 4-9 cm; base convex (rarely to rounded or cuneate); apex rounded to emarginate (shallowly cuspidate); margins entire to slightly revolute (very slightly repand) with 1-5 glands in margins towards base, usually not forming teeth; abaxial surface short-pubescent on midrib (sparsely and inconspicuously pubescent throughout), drying brown to dark brown (olive-tinged); adaxial surface glabrous, drying brown to dark brown (olive-tinged). Inflorescences racemose, lateral (usually not clustered near apices), (1.5-) 2.3-10(-13.5) cm, densely to moderately short-pubescent; peduncle (0.2-) 0.5-4 cm, thick; pedicel 1-5 mm, densely pubescent; bracts broadly ovate, 1.5-2.3 mm, moderately to densely pubescent; bracteoles ovate to lanceolate, 1-2.5 mm (unequal), densely pubescent. Flowers: sepals 5, greenishwhite to yellowish-green, lanceolate-oblong to elliptical (obovate) with acute (to obtuse or rounded) apex, 5-8.4 mm, abaxial surface densely pubescent to sericeous (to moderately so near margins), with a shallow keel usually visible for over half of length; calyx cup funnelform, densely sericeous; sepal glands yellow, irregularly shaped, 1.2-1.4 × 0.7-0.8 mm, upper surface glabrous and wrinkled; petals white to greenish white, obovate to broadly obovate with a narrowed base, round (to rounded-obtuse) apex, 5.5-9 × 3.4-5 mm, slightly longer than sepals, abaxial surface densely sericeous especially along central axis but not prominently keeled, adaxial surface glabrous (sparsely pubescent); filaments white, 2.5-4 mm, glabrous; anthers yellow to brown, 0.5 mm; ovary roundedconic, pilose; styles 3-4, 3- 4 mm, pilose to sericeous at base or for much of length. Seeds possibly 4 or more per fruit (only very young fruit seen).

Vernacular names and uses. – “Fotsiavadika” (Réserves Naturelles 8731); “Hazomborondreo” (Service Forestier 1370); “Mahitsiantjaha” (Service Forestier 21516); “Tsitakonala à g.f. [grands feuilles]” (Service Forestier 15218).

The wood of Homalium nobile is used for construction (Service Forestier 21516).

Homalium nobile is usually native to littoral or low-elevation humid forests, but Antsianaka, the reported location of Humblot 659, is believed to be a locality near Lac Alaotra, well inland at moderate elevation. No more than 10 distinct locations are known, and the littoral forest is fragmented and, outside protected areas, faces continuing loss; hence a preliminary conservation status assessment of “Vulnerable” [VU B2ab(iii)] is appropriate.

Notes. – Sleumer (1973: 325) designated Humblot 33 as lectotype; the collection number was given as 333 by typographical error. The label of the sheet at P does not specify a locality or date, but Humblot’s field book records that this specimen was collected at “Passimbol” on 21 August 1881. Sleumer gave the type locality as “Nosy Varika, Befotaka, ‘Passimbal’ = Ampasimbola”, but this appears to be an error based on the assumption that Passimbal must have referred to the only well-known locality named Ampasimbola (located at 19°49’S 48°22’E). That locality is well inland at an unusually high altitude for H. nobile (ca. 500 m), and, given the roads of the time, it was an inconveniently long distance away from other sites at which Humblot collected around the same time. On 19 August 1881 and 25 August respectively, Humblot made collections at Foulpointe and “Ambatmalam”, which a later annotation to the field books suggests may have been a locality north of Foulpointe. The same annotator suggested that Passimbol was an Ampasimbola located south of Andevoranto (18°55’S 49°08’E) on the east coast, which is not shown on the relatively modern official maps of Madagascar. However, those maps do indicate the existence of an Ampasimbola next to Andondabe (17°45’S 49°22’E), which is only 22 km southwest of Foulpointe [Mahavelona]. This, or someplace nearby, is probably the locality most likely to have been the source of the type collection (and of Humblot 34, a specimen of H. laxiflorum ).

Homalium nobile belongs to the apparently cohesive group of species of eastern littoral or low-elevation forests with racemose inflorescences and pubescent perianths, within which it is distinctive for its sometimes quite large leaves. It is noted above to be most similar to H. brevipedunculatum , which has leaves of a smaller maximum size, normally short inflorescences, and oblanceolate to narrowly obovate petals. The distribution of the two overlaps in Fianarantsoa, and one apparent hybrid specimen is known. The widespread H. laxiflorum also has moderate-sized leaves and smaller flowers; it is distinguished from both H. nobile and H. brevifolium in that the sepals are usually 4 in number, oblong to broad-based obovate with a rounded apex; in normal individuals the petals are substantially longer than the sepals; and the petal indument, though usually dense, is not exceptionally long as in the other two species. The inflorescences of both H. nobile and H. brevipedunculatum are often densely pubescent throughout, though that is not entirely consistent, whereas the inflorescence of H. laxiflorum is typically less pubescent on the proximal portion.

Additional material examined. – Madagascar. Prov. Antsiranana: Sahamalaza-Anovandrano, Masoala, 15°18’45”S 50°20’30”E, 75-150 m, 24.XI.1995, Bernard 145 (MO, P); Distr. Antalaha, canton Ambohitralalana, 15.I.1957, fr., Réserves Naturelles 8731 (P); Masoala, inside park boundary 2 km W of Cap Est, 15°16’23”S 50°27’24”E, 5 m, 23.I.1999, fl., Schatz et al. 3768 (MO, P). Prov. Fianarantsoa: forêt de Mahabo, 23°10”39”S 47°43’06”E, 10 m, 25.IX.2002, fl., Rabenantoandro et al. 1002 (MO); Trail to Analamena, 23°10’45”S 47°42’58”E, 28 m, 8.XI.2004, fl., Randrianasolo et al. 885 (MO); Mahabo, 23°10’39”S 47°42’24”E, 14 m, 11.XI.2002, fl., Razakamalala & Ludovic 333 (MO). Prov. Toamasina: Ambila au S de Tamatave, 10.V.1928, fl., Decary 6494 (P); Station Forestier de Tampolo, 10 km N of Fénérive, 29.XI.1985, fr., Dorr 4396 (P); forêt de Tampolo, près du village Tanambao-Tampolo, 17°17’S 49°25’E, 0-5 m, 5-15.IV.1997, fl., Ralimanana et al. 85 (MO); Ambila-Lemaitso, forest along road from Brickaville a few km before ferry place, 18°49’S 49°08’E, 0-5 m, 11.XI.1999, Randrianasolo & Ranaivojaona 646 (MO, P); Andatsakala, 10.V.1950, fl., Service Forestier 1370 (P); env. de la baie d’Antongil, Anondrivala, au S de Rantabe, I.1954, fl., Service Forestier 8935 (P [4 sheets]); Tampolo, 9.XII.1955, fr., Service Forestier 15218 (P); Mahambo, au S de Fénérive, 30.VIII.1957, fl., Service Forestier 18140 (P); Manambia, Marosoroka, 30.XI.1963, fl., fr., Service Forestier 21516 (MO, P).