Homalium leucophloeum (Tul.) Baill.

Applequist, Wendy L., 2020, A revision of Homalium sect. Rhodonisa (Salicaceae) endemic to Madagascar, Candollea 75 (2), pp. 245-268 : 254-256

5. Homalium leucophloeum (Tul.) Baill. in Bull. Mens. Soc. Linn. Paris 1: 576. 1886.

≡ Nisa leucophloea Tul. in Ann. Sci. Nat., Bot. sér. 4, 8: 72. 1857. ≡ Homalium albiflorum var. leucophloeum (Tul.) Baill. ex H. Perrier in Mém. Mus. Natl. Hist. Nat. 13: 295. 1940.

Holotypus: MADAGASCAR. Reg. Analamanga [Prov. Antananarivo]: env. de Tananarivo, 1840, fl., Goudot s.n. ( G [ G00018421 ] image seen; iso-: P [ P04679197 fragment]!).

= Homalium tetramerum Baker in J. Bot. 20: 110. 1882.

Holotypus: MADAGASCAR: “ Central Madagascar ”, VIII.1880 [com.], fl., Parker s.n. ( K [ K000231485 ] image seen).

Tree to 15(–30) m tall, 40[–48] cm dbh; bark gray to black; twigs pale to grayish (dark) brown, glabrous. Leaves elliptical (ovate, narrowly elliptical), (4.3–)5.2–10(–12.4) × (1.6–)2.1–4.5 (–5.8) cm, moderately thick-textured; margin shallowly repand to subentire (entire); base convex to rounded (short-attenuate); apex short-acuminate to rounded-cuspidate (acute, rounded, emarginate); both surfaces glabrous, usually drying green at least abaxially (rarely brown), darker to blackish adaxially (rarely darker abaxially); secondary veins slightly prominent; petiole sometimes red, (6–)9–14(–27) mm, glabrous. Inflorescences racemose, (1.5–)5–10(–14) cm; peduncle 0.2–1.4(–2.2) cm; rachis glabrous; flowers (1)2–3 per node; flowers sessile (in Cours 5205 pedicels 0.5–1 mm, pubescent). Flowers 4(5)-merous, white to greenish or yellowish white; sepals oblong to broadly oblong, 1.4–2.3[–2.8] mm, glabrous except margins ciliate; sepal glands orbicular or nearly so, 0.5–0.8 × 0.5–0.8 mm; calyx cup shortpubescent (glabrous); petals narrowly obovate, 3–5.6(–6.7[–8]) mm, moderately accrescent, glabrous, margins not ciliate [rarely sparsely short-ciliate]; filaments 1–1.4 mm; anthers broadly elliptical, 0.3 mm high.

Vernacular names and uses. – “Bemahova” (Andrianjafy et al. 1313); “Fandrianakanga” (Service Forestier 2243); “Hazoambo” (Service Forestier 2243); “Hazoambou” (Campenon s.n.); “Hazomainty” (Alleizette 1214); “Hazombato” (Lehavana et al. 257, Ursch 164a, 164b); “Hazomby” (Decary 6243, Parker s.n., Perrier de la Bâthie 6707, 6708, 6709); “Taimboalavo” (Cours 5205); “Zahana à grandes feuilles” (Service Forestier 15063).

Wood is reported to be hard but easy to work, used for construction and for heating and charcoal production (Cours 5205, Service Forestier 16187). An unspecified preparation of the plant is reported to be used to calm the stomach and as a diuretic (Alleizette 1214).

Distribution, ecology and conservation status. – Homalium leucophloeum is native to southeastern to northern humid forests, at least usually mid-elevation to high-elevation, and forests of the central plateau ( Fig. 2 ). It has been reported on limestone, marble, and rocky substrate. It is known from over 10 historical populations, including several protected areas (Itremo, Ankafobe, Ankaratra-Manjakatompo, Andringitra, possibly Midongy du Sud and Montagne d’Ambre).

Its conservation status is therefore assessed as “Least Concern” [LC]. However, it is of concern that recent collections are so few in number, perhaps because of past exploitation for wood.

Notes. – Homalium leucophloeum was accepted by SLEUMER (1973) as a variety of H. albiflorum but is herein reinstated as a species. As for several other segregate species, it is differentiated from H. albiflorum s.s. by its usually 4-merous flowers with glabrous sepal and petal surfaces. Additionally, H. albiflorum has often larger, thin-textured leaves and the flowers are short-pedicellate; its distribution is northern and western, and it occurs at lower altitudes.

The few specimens from the extreme north (DIANA and SAVA regions) have relatively large elliptical, greenish, subentire leaves, sparsely ciliate petals, and in one case larger flowers than any other specimen (extremes of ranges marked with brackets above). These specimens are the only ones in this species or the group of related species that have ciliate petals, and the possibility that they are distinct or, contrarily, reflect some small degree of gene flow from H. albiflorum should be considered. One collection from very high altitude in the southeastern part of the distribution (Rogers 675) is of unusual appearance, with narrow, very long-petioled leaves and numerous racemes; this population may also be genetically distinct.

The isotype at P is marked “Emirna” [Imerina] and gives a date of February 1840, rather than just 1840. Its fragmentary nature strongly suggests that it is a duplicate of the holotype, but the inconsistency of labeling may make this uncertain.

Baron 5551, with modest-sized elliptical leaves, flowers paired in small bracts, glabrous petals, and ciliate sepals, has clear affinities to Homalium leucophloeum (or potentially H. baillonii ). However, it also has 3 mm, relatively densely pubescent pedicels, an unexpected character in either of those eastern species. This is likely to be a hybrid, but the absence of any locality data hinders speculation regarding its parentage.

Additional material examined. – MADAGASCAR. Reg. Amoron’i Mania [Prov. Fianarantsoa]: env. d’Ambatofitor [ah]ana au S d’Ambositra, 1500 m, VI.1912, fr., Perrier de la Bâthie 6710 ( P) ; Itremo, Ambatofinandrahana, forêt d’Atsorakambiaty , 20°35'30"S 46°33'40"E, 1000 m, 7–8.III.1999, fl., Rabenantoandro et al. 68 ( P). Reg. Analamanga [Prov. Antananarivo]: Parc de Tsimbazaza , 18°55'S 47°31'E, 13.II.1985, fr., Barnett et al. 460 ( P) ; Km 26 de la route de Tamatave , 18.X.1951, fl., Benoist s.n. ( P) ; Ambatovory, env. de Tananarive , IV.1957, fl., Bosser 11060 ( MO, P) ; Carion [ Nandihizana ], 1100 m, 30.X.1927, fl., Decary 6026 ( P) ; env. de Tananarive ( Anosivato ), 22.IV.1928, fr., Decary 6243 ( MO, P) ; Ankazobe, forêt d’Ankafobe , 18°08'11"S 47°11'12"E, 1509 m, 23.II.2005, fl., Lehavana et al. 257 (G, K, MO, P) ; jardins et parcs à Tananarive, IV.1913, fl., Perrier de la Bâthie 6707 ( P) ; Parc de Tananarive , IV.1913, fl., Perrier de la Bâthie 6708 ( P) ; jardins et parcs à Tananarive, IV.1913, fl. & fr., Perrier de la Bâthie 6709 ( P) ; sommet du rocher d’Ambatovory, distr. de Tananarive, 16.IV.1949, fl., Service Forestier 610 ( P). Reg. Atsimo-Atsianana [Prov. Fianarantsoa]: Midongy du Sud, 2 km S du village de Beharena II , 23°32'23"S 47°05'07"E, 584 m, 16.IX.2005, fl., Andrianjafy et al. 1313 ( MO) ; massif de l’Ivakoany , montagne Analanavelo, s.d., fr., Cours 5205 ( P) ; village le plus proche Vohilava , Ambomindriha, 13.IV.1956, fl., Service Forestier 16187 ( P). Reg. DIANA [Prov. Antsiranana]: E de la forêt d’Ambre , IX.1926, fr., Perrier de la Bâthie 17699 ( P) ; forêt d’Ambavahibe , IX.s.a., fr., Ursch 164a ( G, P) ; forêt d’Analamera , s.d., fr., Ursch 164b ( P). Reg. Haute Matsiatra [Prov. Fianarantsoa]: Sud-Betsiléo , “wald von Ankafina ”, II.1881, fl., Hildebrandt 3928 ( G, P) ; Andringitra National Park , 22°09'19"S 46°56'41"E, 1750 m, 26.V.2004, fr., Rogers 675 ( G, MO). Reg. Ihorombe [Prov. Fianarantsoa]: Melohavary, Farafangana , 23.V.1950, fl., Service Forestier 2243 ( P). Reg. SAVA [Antsiranana]: Ampahana, Antalaha , 7.IX.1955, fr., Service Forestier 15063 ( P). Reg. Vakinankaratra [Prov. Antananarivo]: Versant E du massif de l’Ankaratra , forêt de Manjakatompo , 24–26.III.1958, fl., Service Forestier 18503 ( P). Reg. Vatovavy-Fitovinany [Prov. Fianarantsoa]: Ambakobe , 1100–1200 m, 9.VI.1881, fl., Lantz s.n. ( P) ; Manakara, s.d., buds, Service Forestier 2738 ( P). Reg. unknown: Imerina Nord , Ambohitraza , s.d., fl., Campenon s.n. ( P) ; Tsarinandriano, VII.1906, fr., Alleizette 1214 ( P) ; sine loco, s.d., fl., Baron 858 ( P).

Specimen incertae sedis. – MADAGASCAR: sine loco, s.d., fr., Baron 5551 ( P).

Figures

Fig. 2. – Map of representative distributions of species in the Homalium albiflorum complex, approximated as necessary.