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L. Watson and M. J. Dallwitz

Akaniaceae Stapf

Excluding Bretschneideraceae.

Habit and leaf form. Small trees (the freshly cut wood and bark with a turnip-like 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. The leaf lamina dorsiventral. Abaxial epidermis papillose. Stomata mainly confined to one surface (confined to depressions in the abaxial surface, being there associated with closely congested, slender papillae with crowned apices). Hairs present to absent (very infrequent). Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Cork cambium present; initially superficial. Primary vascular tissues initially comprising a ring of bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide (with no uniseriates, i.e., unlike Sapindaceae).

The wood semi-ring porous (the growth rings inconspicuous). The vessels moderately small; solitary, radially paired, in radial multiples, clustered, and in tangential arcs. The vessel end-walls oblique; scalariform and simple (only occasional perforation plates scalariform, and these with numerous aberrant arrangements of bars). The vessels without vestured pits; without spiral thickening. The axial xylem without fibre tracheids (the pit borders small and inconspicuous); with libriform fibres; including septate fibres. The parenchyma scanty paratracheal; wood not storied.

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, phytochemistry. Mustard-oils present. Doubtfully cyanogenic (Gibbs 1974). Alkaloids present (one species). Saponins/sapogenins absent. Proanthocyanidins present; cyanidin and delphinidin. Flavonols present; kaempferol and quercetin. Ellagic acid 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 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Brassicales.

Species 1. Genera 1; only genus, Akania.

General remarks. See Hewson 1985, Gadek et al. 1992. Carlquist (1996) considered the wood very like that of Bretschneidera.

Illustrations. • Akania bidwillii: Bot Mag. 8469 (1912). • Technical details: Akania (Hutchinson).

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 16th May 2016.’.