Family Bretschneideraceae

Bretschneideraceae Engl. & Gilg

~ Akaniaceae

Habit and leaf form. Trees (with myrosin cells in bark and inflorescence). Leaves deciduous; alternate; petiolate; compound; (impari-) pinnate. Lamina pinnately veined. Leaves exstipulate.

Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem without fibre tracheids; with libriform fibres; with vessels. Vessel end-walls scalariform and simple (mostly with simple perforations, but some scalariform with aberrant, cross-linking bars — cf. Akania). Primary medullary rays mainly wide. Wood semi-ring porous (the growth rings inconspicuous); parenchyma scanty paratracheal.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes. The ultimate inflorescence unit racemose. Inflorescences terminal. Flowers rather large, or medium-sized; somewhat irregular; slightly zygomorphic. The floral irregularity involving the perianth. Free hypanthium present (the flower perigynous, the corolla inserted on the ‘calyx tube’). Hypogynous disk present; extrastaminal (?); annular.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous; five toothed; campanulate. Corolla 5; 1 whorled; polypetalous; imbricate; unequal but not bilabiate; pink. Petals clawed.

Androecium 8. Androecial members free of the perianth (attached to the nectary disk). Androecium exclusively of fertile stamens. Stamens 8 (declinate); almost diplostemonous; both alternating with and opposite the corolla members; filantherous (the filaments hairy). Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; bi-apiculate. Endothecium developing fibrous thickenings. Anther epidermis persistent (tanniferous). The initial microspore tetrads tetrahedral (usually), or isobilateral. Anther wall initially with more than one middle layer (2 layers). Tapetum glandular. Pollen grains aperturate; (2–)3 aperturate; colpate; 2-celled.

Gynoecium 3(–5) carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 3(–5) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 3(–5) locular. Gynoecium stylate. Styles 1; apical (long, curved). Stigmas 1; capitate. Placentation axile to apical. Ovules 2–3 per locule; pendulous; non-arillate; campylotropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Allium-type. Antipodal cells formed; not proliferating; ephemeral. Hypostase present. Endosperm formation nuclear.

Fruit non-fleshy; dehiscent; a capsule (thick-walled). Capsules obovate, 3(–5) valved. Seeds non-endospermic. Embryo well differentiated (large). Cotyledons 2. Embryo straight. Testa red.

Physiology, biochemistry. Mustard-oils present.

Geography, cytology. Holarctic. China. X = 9.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Capparales (re-assigned from Sapindales). Cronquist’s Subclass Rosidae; Sapindales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid II. APG 3 (2009) Order: Brassicales.

Species 2. Genera 1; only genus, Bretschneidera.

Carlquist (1996) considers the wood very like that of Akania.

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