Family Akaniaceae

Akaniaceae Stapf

Habit and leaf form. Small trees (the freshly cut wood and bark with a turniplike odour). To 8–12 m high. Leaves large (up to 75 cm long); alternate; spiral; leathery; compound; pinnate (imparipinnate, with up to 30 opposite to subopposite, prickly-toothed leaflets); stipulate (the stipules subulate, according to Hewson (1985), though Airy Shaw and Cronquist emphatically state exstipulate).

Leaf anatomy. Abaxial epidermis papillose.

Lamina dorsiventral. Minor leaf veins without phloem transfer cells.

Stem anatomy. Cork cambium present; initially superficial. Secondary thickening developing from a conventional cambial ring. Xylem without fibre tracheids (the pit borders small and inconspicuous); with libriform fibres. Vessel end-walls oblique; scalariform and simple (only occasional perforation plates scalariform, and these with numerous aberrant arrangements of bars). Vessels without vestured pits. Primary medullary rays wide. Wood semi-ring porous (the growth rings inconspicuous); not storied; parenchyma scanty paratracheal.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. Inflorescences axillary (or supra-axillary). Flowers bracteate; fragrant; regular; (4–)5 merous; cyclic; pentacyclic. Free hypanthium present to absent (‘the corolla free or adnate to the calyx’). Hypogynous disk absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; imbricate. Corolla 5; 1 whorled; polypetalous; contorted; regular; white, or pink.

Androecium (5–)8(–10). Androecial members free of the perianth (on the short hypanthium); free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens (5–)8(–10); isomerous with the perianth to diplostemonous; those of the outer whorl oppositisepalous; both alternating with and opposite the corolla members. Anthers (sub-) basifixed; dehiscing via longitudinal slits; latrorse; tetrasporangiate. Endothecium eventually developing fibrous thickenings. Anther epidermis persistent (collapsing). Anther wall initially with more than one middle layer (2–3); of the ‘basic’ type. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colpate; 2-celled.

Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 3 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 3 locular. Gynoecium stylate. Styles attenuate from the ovary; apical. Stigmas 1; 3 lobed. Placentation axile. Ovules 2 per locule; funicled; pendulous; superposed; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Hypostase present. Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule (dull red). Capsules loculicidal. Fruit 3–6 seeded. Seeds endospermic (the endosperm fleshy, smelling of bitter almonds). Cotyledons 2. Embryo straight (massive). Testa yellow.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Mustard-oils present. Doubtfully cyanogenic (Gibbs 1974). Alkaloids present (one species). Proanthocyanidins present; cyanidin and delphinidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent. Saponins/sapogenins absent. Aluminium accumulation not found.

Geography, cytology. Eastern Australia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Capparales (transferred from Sapindales, cf. Gadek et al. 1992). Cronquist’s Subclass Rosidae; Sapindales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid II. APG 3 (2009) Order: Brassicales.

Species 1. Genera 1; only genus, Akania.

Hewson 1985, Gadek et al. 1992. Carlquist (1996) considers the wood very like that of Bretschneidera.

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