Olacaceae

Genera Included: Anacolosa (Blume) Blume, Aptandra Miers, Cathedra Miers, Chaunochiton Benth., Coula Baillon, Curupira Black, Diogoa Exell & Mendonça, Douradoa Sleumer, Dulacia Sleumer, Engomegoma Breteler, Erythropalum Blume, Harmandia Baillon, Heisteria Jacq., Malania Chun & Lee., Minquartia Aublet., Ochanostachys Masters, Octoknema Pierre, Olax L., Ongokea Pierre, Ptychopetalum Benth., Scorodocarpus Becc., Strombosia Blume, Strombosiopsis Engl., and Tetrastylidium Engl..

In collaboration with Valéry Malécot, we have recently completed molecular phylogenetic work on this family. Using a combination of morphology and molecules, the family occurs as two clades, one apparently autotrophic and one containing the species that have been documented as root parasites. We are in the process of publishing these results that will likely require formal circumscription of these two families.

Habit: Terrestrial, mostly evergreen trees, shrubs, and lianas.

Parasitism: Some hemiparasitic (Ximenia) others apparently autotrophic (e.g. Heisteria).

Roots: In parasitic members, forming haustorial connections to a number of different hosts.

Stem: Nodes unilacunar or trilacunar, seldom pentalacunar; commonly with solitary or clustered crystals of calcium oxalate in the cells of the parenchymatous tissues.

Leaves: Alternate, simple, entire; mesophyll often with silicified cells borne singly or in groups and also often with spicular sclereids; stomates of diverse types, sometimes paracytic.

Inflorescence: Small axillary clusters, aggregated into racemes or panicles.

Plant Sex: Flowers bisexual or plants rarely dioecious.

Flowers: Bisexual (rarely unisexual), actinomorphic, dichlamydous, hypogynous, 1/2 epigynous, or seldom epigynous or perigynous.
Calyx: Small, more or less cupular, inconspicuously 3-6-toothed (or teeth absent), often accrescent in fruit.
Corolla: Petals 3-6, alternate with the calyx lobes, valvate (rarely imbricate), free or connnate below or forming a corolla tube (as in Schoepfia).
Nectary: Nectary-disk intrastaminal, surrounding the ovary or surrounding the style at the top of the ovary.
Androecium: As many as and opposite the petals or 2-5 times as many as the petals but all apparently in a single cycle; filaments free, often adnate to the base of the corolla or connate into a sheath around the style; anthers tetrasporangiate and dithecal, dehiscence by longitudinal slits or seldom by terminal valves.
Staminodia: Occur opposite, alternate, or opposite and alternate of the petals.
Pollen: 2-3 nucleate, of diverse forms, variously tricolpate, tricolporate, or 3-8 porate.
Gynoecium: Compound ovary, superior to inferior with terminal style and a 2-5-lobed stigma; ovary 2-5 locular at the base but mostly unilocular above.
Ovule: Solitary in each locule or semilocule, pendulous from the top of a free-central (or partly or wholly axile) placenta (in Octoknema the placenta joins the top of a unilocular ovary); anatropous or seldom orthotropous, bitegmic or unitegmic and tenuinucellar or nearly so or not differentiated into nucellus and integuments.
Embryo, etc.: Monosporic embryo sac or seldom bisporic; 8-nucleate; endosperm development cellular or helobial; embryology diverse (Allium and Polygonum types in Olax). In Olax, the primary endosperm nucleus divides to form the first transverse wall of the embryo sac (Kuijt 1968).

Fruit: A drupe or nut, often enclosed in the accrescent calyx; almost always 1-seeded.

Seed: With thin testa, small or tiny embryo near the tip of the copious, oily, and sometimes also starchy endosperm; cotyledons 2-6.

Chromosomes: X = 19, 20.

Alternate Family Names: Cathedraceae, Chaunochitonaceae, Coulaceae, Erythropalaceae, Heisteriaceae, Octoknemaceae, Schoepfiaceae, Scorodocarpaceae, Strombosiaceae, Tetrastylidiaceae.

Link to Family Description in Delta