Family Aquilariaceae

Aquilariaceae R. Br.

~ Thymelaeaceae

Habit and leaf form. Trees. Leaves alternate; flat; petiolate; non-sheathing; not gland-dotted; simple. Lamina entire; pinnately veined. Leaves exstipulate. Lamina margins entire.

Stem anatomy. Cork cambium present; initially superficial. Internal phloem present. Secondary thickening anomalous; from a single cambial ring. ‘Included’ phloem present. Vessels with vestured pits. Primary medullary rays narrow. Wood parenchyma paratracheal.

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or polygamomonoecious (?).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in umbels, or in corymbs, or in fascicles, or in panicles. Inflorescences terminal and axillary; subsessile axillary umbels or fascicles, these sometimes subpaniculate. Flowers ebracteate; regular; cyclic; tetracyclic, or pentacyclic. Free hypanthium present. Hypogynous disk absent.

Perianth with distinct calyx and corolla (but the corolla often scalelike), or sepaline; (8–)10; 1 whorled, or 2 whorled; isomerous (when corolla present, but the petal scales sometimes bilobed). Calyx (4–)5; 1 whorled; gamosepalous; (4–5) blunt-lobed; campanulate, or funnel-shaped, or tubular, or hypocrateriform; regular; imbricate. Corolla when present, (4–)5; 1 whorled; polypetalous, or gamopetalous (the petals represented by scales at the mouth of the hypanthium/calyx tube, sometimes connate at the base, sometimes bilobed).

Androecium (4–)5, or (8–)10. Androecial members free of the perianth (borne on the hypanthium); all equal, or markedly unequal; free of one another; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens (4–)5, or (8–)10; isomerous with the perianth, or diplostemonous; when in two cycles, oppositisepalous (i.e. the upper, outer cycle opposite the sepals); filantherous (the filaments short). Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen grains aperturate; 4–12 aperturate; foraminate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 2 celled. Gynoecium syncarpous (but tending to pseudomonomery); eu-syncarpous; superior. Ovary 2 locular (sometimes incompletely so); subsessile to stipitate. Gynoecium non-stylate to stylate. Styles when present, 1; apical; much shorter than the ovary. Stigmas 1; large, capitate, or subpeltate. Placentation axile to apical. Ovules 1 per locule; funicled; pendulous; hemianatropous, or anatropous; bitegmic; crassinucellate. Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 1 seeded, or 2 seeded. Seeds endospermic. Embryo well differentiated. Cotyledons 2. Embryo straight.

Geography, cytology. Tropical. Eastern tropical Africa to New Caledonia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Thymelaeales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 (2009) Order: Malvales (?).

Species 32. Genera 6; Aquilaria, Gyrinops, Gyrinopsis, Microsemma, Octolepis, Solmsia.

Economic uses, etc. Timber and paper fibre from Gyrinops, incense from Aquilaria.

Illustrations.
• Technical details: Aquilaria (Lindley).

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