Homalium sect. Nisa (Noronha ex Thouars) Baill. ex Warb.

Wassel, Anna C. & Applequist, Wendy L., 2020, A revision of Homalium sect. Nisa (Salicaceae) endemic to Madagascar, Candollea 75 (1), pp. 1-23 : 3-4

Homalium sect. Nisa (Noronha ex Thouars) Baill. ex Warb.

in Engl. & Prantl, Nat. Pflanzenfam. 98–99: 36. 1893.

≡ Nisa Noronha ex Thouars , Gen. Nov. Madagasc.: 24. 1806. ≡ Homalium [unranked as §] Nisa (Noronha ex Thouars) Baill. in Bull. Mens. Soc. Linn. Paris 1: 575. 1886.

Typus (designated by SLEUMER, 1973: 295): Homalium nudiflorum (DC.) Baill. (≡ Nisa nudiflora DC. ).

Stipules opposite the petiole base and fused (in H. intercedens Sleumer axillary, free), usually caducous. Leaves with venation more or less brochidodromous. Inflorescences spicate; bract and bracteoles large, usually broad, thicktextured, persistent. Flowers sessile (rarely subsessile); perianth 5–6(–8)-merous. Sepals obovate to oblanceolate (to nearly ligulate), oblanceolate-oblong or narrowly elliptic (in H. louvelianum H. Perrier oblong-ovate to ovate-deltoid), spreading, accrescent (only slightly so in H. louvelianum ); calyx tube short, broadly funnelform to cup-shaped, or in fruit hemispherical. Petals ovate to oblong, usually smaller than sepals, modestly accrescent and curving over fruit (in H. louvelianum similar to sepals in size and spreading); sepals and petals not ciliate, or ciliolate in conjunction with overall surface pubescence. Sepal glands large, elliptic to elongated oblong-elliptic or roughly trapezoidal. Stamens 1 per petal, inserted between glands; anthers dorsifixed, broadly oblongelliptic with oblong-elliptic locules and a large connective, the slits of dehiscence nearly parallel. Upper surface of ovary often nearly flat in flower, in fruit becoming hemispherical or broadly conical; styles 3–4, fused basally (rarely fused for most of length). Locule of fruit subglobose or vertically compressed, internally glabrous (short-pubescent); seeds sometimes 1 per fruit, subglobose, largely filling the locule (or several small immature seeds, possibly most never maturing).

Key to the species of Homalium sect. Nisa

1. Sepals about equal to petals at anthesis, broadly oblongovate (to ovate-deltoid), in fruit slightly accrescent, <3.5 mm and only modestly longer than petals; petals not curving inward over fruit ............. 5. H. louvelianum

1a. Sepals longer than petals at anthesis, oblanceolate to narrowly oblong-oblanceolate, spatulate, narrowly elliptic, or nearly ligulate (in flower obovate to elliptic), in fruit conspicuously accrescent,> 3.5 mm and much longer than petals; petals usually curving inward as fruit matures .... 2

2. Sepal glands densely pubescent on upper (inward-facing) surface ............................................... 10. H. stelliferum

2a. Sepal glands glabrous or glabrate throughout .............. 3

3. Leaves lanceolate; stipules free ............ 4. H. intercedens

3a. Leaves elliptic, oblong-elliptic, obovate or oblanceolate (rarely to ovate, very rarely a few lanceolate); stipules fused, opposite petioles ................................................ 4

4. Calyx densely pubescent to sericeous at least on cup, basal portion of abaxial sepal surface .................................... 5

4a. Calyx glabrous or sparsely pubescent, often more densely short-pubescent on cup, with trichomes confined to medial or marginal areas of one or both sepal surfaces ............. 7

5. Leaves elliptic to narrowly elliptic, obovate, or oblanceolate, (2.5–)3–6(–9) × 1.3–2.5(–3) cm, without marginal glands; bracts and bracteoles often ciliate, pubescent only along midrib or glabrous; adaxial surface of sepals glabrous; petals 1.5–2.5 mm, densely pubescent abaxially (to sparsely at margins), densely to sparsely pubescent adaxially; filaments 0.9–1.1 mm, anthers 0.2–0.3 mm ............ .................................................................... 11. H. tenue

5a. Leaves elliptic to broadly or narrowly elliptic or obovate, (3.3–)5–9.5 × (1.8–)2–4.5(–5.4) cm, usually with inconspicuous marginal glands; bracts and bracteoles ciliate and usually pubescent throughout (mostly along midrib); adaxial surface of sepals short-pubescent at least basally; petals 2–5 mm, velutinous on both surfaces; filaments (1.2–) 1.9–2.8 mm, anthers 0.4–0.65 mm ..................... 6

6. Flowers mostly borne in pairs or closely clustered; bracts and bracteoles 3.5–5 mm; calyx cup long-sericeous, both sepal surfaces densely pubescent; southern Madagascar............................................................. 2. H. ciliolatum

6a. Flowers usually borne singly; bracts and bracteoles 1.5– 2.5(– 3) mm; calyx cup densely pubescent, sepals densely pubescent towards base of both surfaces, becoming sparsely pubescent (to glabrous) near apical margins; northeastern Madagascar............... 1. H. antilahimenae

7. Petioles (10–) 15–30 mm; inflorescences paniculate, pubescent; flowers mostly paired ...................... 9. H. retusum

7a. Petioles 3–15 mm; inflorescences racemose or paniculate, glabrous or seldom sparsely or patchily pubescent; flowers borne singly ................................................................. 8

8. Leaves oblanceolate, (2.7–)3.4 – 6.8 × (0.9 –) 1.1 –2 cm, with revolute margins; inflorescences racemose, (0.5–)1–2.5(–3.3) cm; filaments 0.5–0.8 mm, anthers ca. 0.2 mm .............................................. 6. H. mandenense

8a. Leaves elliptic to broadly or narrowly elliptic, oblong-elliptic, or obovate (to oblanceolate in H. nudiflorum ), 4.9–16 × 1.5–9 cm, with entire (sometimes partly, not strongly revolute), crenate, or serrate to dentate margins; inflorescences racemose or paniculate, (2–) 3– 12 cm; filaments 1.6–3.1(–3.7) mm, anthers (0.3–)0.5–0.7(–0.8) mm ..... 9

9. Leaves (5 –)6 – 16 × (1.8 –)3 – 6.2(– 7) cm with petiole 3–7(–10) mm; leaf margins usually prominently toothed

(subentire) with elongated glands in tooth apices; both surfaces of petals densely (to moderately) pubescent especially on apical half; humid forests to drier central forests, at elevations of 445–1860 m ................. 3. H. confertum

9a. Leaves 4.9– 14.5 × 1.5–7 cm with petiole (3–)4–13(–15) mm; leaf margins entire to repand (crenulate, partly somewhat revolute), with glands small and round or absent; petals usually moderately (to densely) pubescent only at apex of one or both surfaces (rarely on entire apical portion), otherwise sparsely pubescent with often ciliate margins, or glabrous; humid (to littoral) forests, at elevations of 12–1220 m ............................................ 10

10. Leafing internodes (1.7 –)2– 4(–5,5) mm diam.; leaves 8.5– 14.5 × 5 –7 cm; inflorescences paniculate; petals in fruit 3–5.6 mm ................................. 8. H. pachycladum

10a. Leafing internodes (0.9–)1.1–2.4(–3.2) mm diam.; leaves 4.9–9(–10.5) × 1.5–4.2(–5.4) cm; inflorescences racemose (paniculate); petals 1.5–4 mm .............. 7. H. nudiflorum