Family Brexiaceae

Brexiaceae Lindl.

~ 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 evergreen; alternate; leathery; petiolate; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate. Lamina margins entire, or serrate, or dentate (sometimes prickly).

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

Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls scalariform and simple, or simple. Wood parenchyma apotracheal.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence unit 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, biochemistry. 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 (1998) Eudicot; core Eudicot; Rosid; unassigned to Eurosid I or Eurosid II, or Eurosid I. APG 3 (2009) Order: Celastrales.

Species 10. Genera 1; Brexia.

Illustrations.
• Technical details: Brexia with Ixerba.
• Technical details: Brexia (Lindley).
• Brexia spinosa: Bot. Reg. 872, 1825.

Miscellaneous. This sensu stricto description (prepared by LW in 2009) needs checking against standard references for pollen and phytochemistry.

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