Olax

Rogers, Zachary S., Malécot, Valéry & Sikes, Kendra G., 2006, A synoptic revision of Olax L. (Olacaceae) in Madagascar and the Comoro Islands, Adansonia (3) 28 (1), pp. 71-100 : 74-75

Genus Olax L.

Species Plantarum 34 (1753). — Type: Olax zeylanica L.

Fissilia Comm. ex Juss. , Genera Plantarum 260 (1789). — Type: Fissilia psittacorum Lam.

Pseudaleia Thouars , Genera Nova Madagascariensia 15 (1806), nom. illeg.

Pseudaleia Thouars ex DC. , Prodromus 1: 533 (1824). — Type: Pseudaleia madagascariensis DC.

Pseudaleioides Thouars , Genera Nova Madagascariensia 15 (1806). — Type: Pseudaleioides thouarsii DC.

DESCRIPTION

Hemiparasitic shrubs or trees, rarely lianas; secondary roots with lateral haustoria. Branches exstipulate, usually 4-sided, ± winged in cross section, longitudinally striate, 2 or 4 decurrent lines originating at leaf scars; young branches often zig-zag. Leaves simple, alternate-distichous, rarely decussate, glabrous, margin entire; venation pinnate; secondary veins anastomosing in brochidodromous loops near the margin; fine venation irregularly reticulate; petioles articulate. Inflorescences axillary, racemose, pseudosolitary, or solitary, sometimes ramified with bracts subtending ramifications; axes often zig-zag; bracts usually small and early caducous, sometimes persistent and becoming large and foliose. Flowers hermaphroditic or rarely unisexual, tubular, actinomorphic; calyx cupuliform and small at anthesis, often accrescent in fruit, margin entire to denticulate; corolla with 3 to 6 (7) petals; petals valvate, free or attached by their bases at anthesis, sometimes irregularly fused, upper one-half to one-third of the petal abaxially decurved, glabrous adaxially (except papillate with a small uncinate thickening near apex of lobes), glabrous abaxially; petal ligule (i.e. membranous protuberance between petal and base of free portion of stamen) often present; androecium in one or two whorls, each whorl consisting of various permutations of stamens and staminodes; stamens most often 3 to 6 (7); filaments partially fused to corolla; anthers bilocular, introrse, basifixed,longitudinally or rarely apically dehiscent; staminodes bifid, most often 3 to 6 (7), generally longer than fertile stamens; glandular zone (i.e. nectary disc) minute, surrounding the base of the ovary; ovary superior or semi-inferior (i.e. partly nested in the glandular zone), 1-locular (or 3-locular near the base of the locule), placenta central and basally inserted in a column subtending 1 to 3 ovules; ovules pendulous, anatropous, tenuinucellate, uni- or ategmic; style either short or long; stigma capitate, usually 3-lobed. Fruits drupaceous, 1-seeded, sometimes completely surrounded by an accrescent calyx; persistent style short; mesocarp ± developed; endocarp coriaceous. Seeds with copious, oily endosperm.

KEY TO THE SPECIES OF OLAX L. IN MADAGASCAR AND THE COMORO ISLANDS (see Table 1 for a summary of flower and fruit variation)

1. Petals 3, rarely 4; calyx not accrescent in fruit ............................................................. 2 — Petals 5 or 6, rarely 4; calyx accrescent in fruit ............................................................ 4

2. Leaves lanceolate or narrowly elliptic, (3-)4-8 times longer than broad; apex narrowly acute; base cuneate ............................................................................... 5. O. lanceolata

— Leaves ovate, obovate, or broadly elliptic, 2-3(-3.5) times longer than broad; apex acuminate, acute, broadly rounded, obtuse, or emarginate; base broadly rounded, obtuse, or acute .......................................................................................................................... 3

3. Leaves 4.5-11.5 cm long, ovate, rarely elliptic; apex acuminate, rarely acute; venation generally visible on both surfaces; fruits spheroid ....................... 6. O. madagascariensis

— Leaves 1-4.2 cm long, obovate, rarely elliptic or ovate; apex broadly rounded, obtuse, emarginate, or rarely acute; venation inconspicuous abaxially, or only the secondaries faintly visible; fruits obovoid ................................................................. 2. O. capuronii

4. Fertile stamens 3, rarely 4 or 5; accrescent calyx crustaceous or semi-fleshy, completely surrounding the fruit .................................................................................................. 5

— Fertile stamens 6, rarely 5 or 7; accrescent calyx chartaceous, only surrounding the base of the fruit (c. 7-11 mm in diam.) .............................................................................. 7

5. Leaves coriaceous; venation inconspicuous, or only secondaries faintly visible; petioles

darker than midribs; fruits 12-17 mm in diam. ................................... 4. O. emirnensis — Leaves semi-succulent, membranous-chartaceous, or largest leaves becoming chartaceous;

venation usually distinct; petioles not darker than midribs; fruits 6-9 mm in diam. .... 6

6. Leaf blades 2-5 cm long, 1-2 cm wide, semi-succulent or membranous-chartaceous; petioles c. 0.5 mm in diam.; floral pedicels longer than corolla, rarely of equal length, 0.3-0.5 mm in diam.; fruits ellipsoid or spheroid [plants of Madagascar and Africa] ..... ............................................................................................................. 3. O. dissitiflora

— Leaf blades 4.2-10 cm long, 1.3-4.5 cm wide, chartaceous, or only the leaves near the tips of the branches membranous-chartaceous; petioles 1-2 mm in diam.; floral pedicels shorter than corolla, c. 1 mm in diam.; fruits ovoid [plants of Mayotte] .......... 7. O. mayottensis

7. Leaves 5-12 cm long (true leaves only, leafy organs in pseudosolitary inflorescences are foliose bracts); blades abaxially glaucous; apex acute and usually mucronate, rarely obtuse or rounded; petal ligule 0.6-1 mm long, densely pubescent .................... 8. O. thouarsii

— Leaves 1.5-4 cm long; blades not glaucous; apex emarginate; petal ligule 0-0.3 mm long, sparsely pubescent ............................................................................ 1. O. antsiranensis