Homalium stelliferum H. Perrier

Wassel, Anna C. & Applequist, Wendy L., 2020, A revision of Homalium sect. Nisa (Salicaceae) endemic to Madagascar, Candollea 75 (1), pp. 1-23 : 16-18

10. Homalium stelliferum H. Perrier in Mém. Mus. Natl. Hist. Nat. 13: 293. 1940.

Holotypus: MADAGASCAR. Prov. Toamasina: “ Tanatanampotsy, forêt littorale orientale ”, s.d., fr., Perrier de la Bâthie 14920 (leg. Louvel) ( P [ P04734366 ]!) .

Tree to 30 m tall, 80 cm dbh; twigs pale to grayish or dark brown, glabrous to short-pubescent or pilose,, leafing internodes 1 –4.2 mm diam.; stipules fused, caducous. Leaves narrowly oblong-elliptic to oblong-oblanceolate, oblanceolate, elliptic, or obovate, 3.6–13.7 × 1.3–6.6 cm, coriaceous; base convex to rounded or cuneate; apex cuspidate to rounded, obtuse or acute, or emarginate (short-acuminate); margin subentire to inconspicuously toothed (dentate, somewhat revolute), usually with some glands in marginal convexities; secondary veins 7–11 per side; adaxial surface glabrous or bearing few trichomes on midrib, abaxial surface sparsely pilose to sparsely pubescent or glabrous, drying brown (to grayish green) or greenish brown to blackened on adaxial surface, lighter or medium brown (to green) on abaxial surface; petiole pilose, short-pubescent or glabrous, (2–) 3–13 mm. Inflorescences racemose, axillary, (2.5–) 4.5–9.5 cm; rachis densely to moderately (sparsely) pubescent or pilose; bracts and bracteoles usually with ciliate margin, densely to moderately pubescent (pilose, glabrate) or sparsely pubescent to glabrous, 2.3–4.5 mm; flowers borne singly. Flowers 5–6(7)- merous, greenish; sepals narrowly elliptic to narrowly oblongelliptic, oblanceolate or oblanceolate-oblong, 6.6–8.4 mm after anthesis, 9.4–12 mm in fruit, glabrous or with dense appressed pubescence on calyx cup, dense to sparse pubescence in medial portion of one or both sepal surfaces; sepal glands pubescent on upper (inward-facing) surface; petals oblong-ovate to elliptic, 3.5–4 mm after anthesis to in fruit, both surfaces densely (to moderately) pubescent at least on apical half; filaments sparsely pubescent to sparsely pilose, 1.6–2.5 mm; anthers 0.6–0.8 mm; styles ca. 2.4–3.4(–4?) mm.

Notes. – Homalium stelliferum is distinguished from all other species of sect. Nisa by having dense pubescence on the upper surface of the sepal glands, which is typically turned to face inward as the outer edge of the gland is elevated. In addition, the leaves are often sparsely pilose or pubescent, and sometimes the twigs and petioles are as well. Trichomes are also seen on the filaments, which is rare but not unknown in other species. Although limited material of H. stelliferum is known, it is quite variable in characters including leaf size and shape and the indument of several parts. A population from the northern extreme of the range with relatively large, broad, and long-petiolate leaves is herein segregated as H. stelliferum subsp. andapense Wassel & Appleq. This population’s range of variation for key characters overlaps with that of subsp. stelliferum , which is not unusual in infraspecific taxa, but its typical appearance is sufficiently different from normal H. stelliferum that it is very likely to be genetically distinct to some degree.

Key to the subspecies of Homalium stelliferum

1. Leaves narrowly oblong-elliptic to oblong-oblanceolate or oblanceolate (rarely obovate), 3.6–11.5 × 1.3–4.5(–5.5) cm; leafing internodes of twigs 1–2.7 mm diam.; petiole (2–)3–5(–10) mm; bracts densely to moderately pubescent (rarely to glabrate or pilose); calyx densely pubescent basally to glabrous ............ 10a. H. stelliferum subsp. stelliferum

1a. Leaves elliptic to obovate, 6.3–13.7 × 3.1–6.6 cm; leafing internodes of twigs 2–4.2 mm diam.; petiole 6–13 mm; bracts sparsely pubescent to glabrous; calyx glabrous ...... .............................. 10b. H. stelliferum subsp. andapense