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The families of flowering plants

L. Watson and M.J. Dallwitz

Brexiaceae Lindl.

~ Celastraceae (Escalloniaceae or Grossulariaceae in older texts).

Excluding Ixerbaceae, Rousseaceae.

Habit and leaf form. Small trees, or shrubs; resinous (at least sometimes), or not resinous. Leaves persistent; alternate; leathery; petiolate; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate. Lamina margins entire, or serrate, or dentate (sometimes prickly).

Leaf anatomy. The leaf lamina dorsiventral. The mesophyll without raphides. Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls scalariform and simple, or simple. The parenchyma apotracheal. ‘Included’ phloem absent.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence units cymose. Inflorescences terminal and axillary (few flowered); few-flowered cymes. Flowers medium-sized to large; regular; 4–6 merous; cyclic; tetracyclic. Free hypanthium present to absent (with slight perigyny).

Perianth with distinct calyx and corolla; 8–12; 2 whorled; isomerous. Calyx (4–)5(–6); 1 whorled; briefly gamosepalous, or polysepalous. Calyx lobes markedly longer than the tube. Calyx regular; persistent; imbricate. Corolla (4–)5(–6); 1 whorled; polypetalous; contorted; regular; plain; persistent, or deciduous; non-accrescent. Petals shortly clawed; entire.

Androecium 4–6, or 8–12 (i.e., interpreting interstaminal, palmately branched scales as staminodal). Androecial members branched (with regard to the interstaminal, staminodial scales); free of the perianth; markedly unequal (the scales being much shorter than the stamens); basally coherent (the bases of the filaments connected by those of the scales); 1 whorled. The androecial bundles (i.e., the branched scales,) opposite the corolla members. Androecium including staminodes (again, referring to the interstaminal scales). Staminodes 4–6, or 25–36 (depending on interpretation); in the same series as the fertile stamens; more or less petaloid. Stamens (4–)5(–6); isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous. Anthers dorsifixed; dehiscing via longitudinal slits; introrse. Pollen shed in aggregates; with viscin strands (the grains cohering). Pollen grains aperturate; 3–5 aperturate; colporate; 3-celled.

Gynoecium 5 carpelled. Carpels (usually?) isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 5 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1; 5 lobed; truncate; dry type; non-papillate; Group II type. Placentation axile. Ovules 12–50 per locule (to ‘many’); funicled; horizontal; apotropous; biseriate; non-arillate; anatropous; bitegmic; crassinucellate (in that the megaspore mother-cell in B. madagascariensis cuts off a primary parietal cell which divides only anticlinally to form a single parietal layer). Endothelium differentiated. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids elongated. Endosperm formation nuclear.

Fruit fleshy, or non-fleshy; indehiscent; a drupe (5-sided, with papillose epicarp and bony endocarp). The drupes with one stone (one-celled). Seeds almost non-endospermic. Cotyledons 2. Embryo straight.

Physiology, phytochemistry. Not cyanogenic.

Geography, cytology. Paleotropical. Sub-tropical to tropical. East Africa, Madagascar, Seychelles.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Saxifragales. Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Celastrales (as a synonym of Celastraceae?).

Species 10. Genera 1; Brexia.

History of the encoded description. This sensu stricto description (prepared by LW in 2009) needs checking against standard references for pollen and phytochemistry. As it stands it differs from that of Celastraceae (q.v.) in the contorted corolla, branched androecial members with petaloid staminodes in the same series as the fertile stamens, the single stigma, and the horizontal, non-arillate ovules.

Illustrations. • Le Maout and Decaisne: Brexia with Ixerba. • Brexia madagascariensis: Lindley. • Brexia spinosa: Bot. Reg. 872, 1825. • Thomassetia seychellana, cf. Brexia: Hook. Ic. Pl. 28 (1902).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or 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). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.