Homalium longiracemosum Appleq., 2018

Applequist, Wendy L., 2018, A revision of the Malagasy species of Homalium sect. Blackwellia (Salicaceae), Candollea 73 (2), pp. 221-244 : 232-235

8. Homalium longiracemosum Appleq. , spec. nova ( Fig. 3 ).

Holotypus: MADAGASCAR. Prov. Toliara: Anosy Rég ., Distr. Taolagnaro , Cne Mahatalaky , Fkt. Sainte Luce , forêt littorale d’Analavinaky , située à l’W du village d’Ambandrika au bord de la riv. de Rianabo , 24°43'21"S 47°00'44"E, 143 m, 24.XI.2009, post-fl., Rakotovao 4714 ( MO-6481608! ; isotype: TAN).

Homalium longiracemosum Appleq. is distinguished from other Malagasy species of Homalium sect. Blackwellia in having leaves mostly narrowly lanceolate to narrowly elliptical, 7.3–15 × 2.6–3.9 cm with petiole (6.5–) 9–18 mm, racemose inflorescences 9–25 cm long, and pubescent sepal glands.

Tree to 18 m, 45 cm dbh; young twigs glabrous. Leaves narrowly oblanceolate to narrowly elliptical (obovate-elliptical), 7.3–15 × 2.6–3.9 cm; petiole (6.5–) 9–18 mm; base convex to cuneate; apex short-acuminate to cuspidate (acute); margins shallowly repand, undulate or crenate-serrulate, with glands elongated, prominent at tooth apices; adaxial surface drying dark brown, abaxial surface medium brown. Inflorescences racemose, lateral, 9–25 cm, short-pubescent; flowers pedicellate with pedicels 0.5–2(–3.5) mm; bracts linear to narrowly oblong, c. 1.5–2 mm. Flowers 6-merous; calyx tube funnelform, sparsely short-pubescent to glabrate; sepals narrowly oblanceolate (to narrowly oblong) with acute apex, 1.8– 3.8 mm; petals narrowly lanceolate to narrowly oblong with acute apex, 2.5– 3.8 mm; sepals and petals yellowish green, accrescent, moderately longer than calyx tube, in fruit ascending (partly and irregularly reflexed), ciliate with straight well-separated hairs, both surfaces glabrous or glabrate; sepal glands shortpubescent; filaments 1.6–2.5 mm, glabrous; ovary moderately pubescent with thick straight hairs; styles 4, c. 1.6 mm, basally pubescent.

Candollea 73, 2018 Homalium sect. Blackwellia (Salicaceae) in Madagascar – 233

Vernacular name. – “Varikanda” (Rakotovao 4714).

Distribution, ecology and conservation status. – The two known collections of H. longiracemosum are from a small region in extreme southeastern Madagascar, where they occur in lowaltitude humid forest. Though both are indicated in TROPICOS (2018) to be from the protected area of Tsitongambarika, the very small Area of Occupancy (8 km ²), with two populations in very close proximity, supports a conservation status of “Vulnerable” [VU D2].

Notes. – Homalium longiracemosum is distinguished from other species of sect. Blackwellia with pubescent sepal glands and racemose inflorescences by its long, narrow, long-petioled leaves and long sturdy racemes.

Both known specimens, which were collected around the same time but from two different localities, evince an unusually high level of insect damage.

Paratypus. – MADAGASCAR. Prov. Toliara: Taolagnaro , Mahatalaky , Farafara Vatanibe , forêt humide à haute futaie à l’W du village de Malama , au bord de la grande riv. Belomotse , 24°51'02"S 47°00'20"E, 135 m, 14–18.XI.2009, fl., Rakotovao et al. 4513 ( MO).

Figures

Fig. 3. – Homalium longiracemosum Appleq. A. Flowering branch; B. Flowers. [Rakotovao 4714, TAN] [Drawing: R.L. Andriamiarisoa]