Homalium boinense H. Perrier

Wendy L. Applequist, 2016, Revision of the Malagasy species of Homalium sect. Eumyriantheia Warb. (Salicaceae), Candollea 71 (1), pp. 33-60 : 37

1. Homalium boinense H. Perrier in Mém. Mus. Natl. Hist. Nat. 13: 297. 1940.

Lectotypus (first step, designated by Sleumer, 1973: 318): Madagascar. Prov. Mahajanga: Beritzoka entre Maevatanana et Andriba , X.1892, fl., Perrier de la Bâthie 338 ( P).

Lectotypus (second step, designated here): Madagascar. Prov. Mahajanga: Beritzoka entre Maevatanana et Andriba , X.1892, fl., Perrier de la Bâthie 338 ( P [ P04679008 ]!; isolecto-: G [ G00018416 ] image seen, L [ L0010885 ] image seen, P [P04679009]!). Syntypi: Madagascar. Prov. Mahajanga: sine loc., 1898, fl., Perrier de la Bâthie 699 ( P [ P04679004 ]!, S [ S10-10098 ] image seen) ; env. de M[a]evatanana, 1900, fl., Perrier de la Bâthie 6729 ( P [ P04679005 ]!, PRE [ PRE0602253 -0] image seen, US [ US00603577 ] image seen) ; Mahamavo, W du Namakia , IX.1922, fl., Perrier de la Bâthie 14833 ( K [ K000231474 ] image seen, P [ P04679006 , P04679007 ]!).

Tree to 20 m tall; large twigs brown; young twigs brown, glabrous or sparsely and minutely pubescent; stipules broadly deltoid (deltoid), 1-1.6 mm, minutely pubescent or glabrous. Leaves alternate; petiole 5-15 mm, glabrous or sparsely minutely pubescent; blade elliptical to broadly elliptical or obovate, 5.7-13.6 × 3.4-6.6 cm; base rounded (minutely attenuate at petiole attachment) to convex (cuneate in immature leaves); apex rounded to rounded-obtuse or cuspidate; margins subentire or shallowly wavy or toothed, then with small glands in tooth apices at margin; abaxial surface glabrous or bearing few small hairs on midrib, drying brown; adaxial surface glabrous, drying dark or pale grayish brown. Inflorescences narrowly paniculate, with flower clusters usually borne on short branches or flowers solitary distally, occasionally racemiform, lateral, 6.5-15 cm, short-pubescent; peduncle (0.8-) 2-5.5 cm, moderately thick; pedicel 1-2(-2.5) mm, densely short-pubescent; bracts ovate to broadly deltoid or suborbicular, 1.3-3.4 mm, densely (to sparsely) pubescent; bracteoles lanceolate (ovate), 1-2 mm, pubescent. Flowers: sepals 5(-6), narrowly oblong to narrowly elliptical or oblong-ovate with acute to rounded-acute (rounded) apex, 3-5.7 mm, abaxial surface moderately pubescent; calyx cup shortly funnelform, densely short-pubescent especially basally; sepal glands irregularly trapezoid to rectangular with a depressed center, 0.6-1.3 × 0.5-0.8 mm, upper surface usually densely short-pubescent; petals white, obovate to oblanceolate, with rounded apex, 5.2-8 × 2.3-4 mm, conspicuously longer than sepals, abaxial surface densely short-pubescent especially basally, adaxial surface glabrous; stamens in groups of 5; filaments 3-4 mm, glabrous; anthers 0.4 mm; ovary raised conic, densely short-pubescent; styles 4, 1.4-2.3 mm, short-pubescent at base. Seeds not seen.

Uses. – The wood is said to be white, of good quality, and much used (Perrier de la Bâthie 14833).

Distribution, ecology and conservation status. – Homalium boinense is confined to dry forest in Mahajanga province. It is known from fewer than 5 locations; its native range is unprotected and highly degraded, and it has not been collected for over 90 years. A preliminary conservation status assessment of “Endangered” [EN B2ab(iii)] following IUCN Red List Categories and Criteria probably underestimates the level of threat.

Notes. – Sleumer (1973) designated Perrier de la Bâthie 338 at P as the lectotype of Homalium boinense ; there are two sheets of this collection at P, both of which he marked “Syn & Lectotype ”. Art. 9.17 of the ICN ( McNeill et al., 2012) recommends that a second-stage lectotypification be published to select one of these sheets; the selected sheet is in better condition and includes a fragment packet and what is probably Perrier de la Bâthie’s original label.

Homalium boinense is notable for its stamens in groups of five, rather than three, and its habitat in dry regions of Mahajanga province, where no other species of sect. Eumyriantheia occur.