| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Ixerbaceae Griseb. ex Doweld & Reveal

~ Strasburgeriaceae (APG), formerly Brexiaceae, Escalloniaceae, etc.

Habit and leaf form. Small, glabrous trees (to about 15 m high); non-laticiferous, without coloured juice. Mesophytic (in hilly forests). Leaves persistent; medium-sized (about 6–15 cm long); mostly sub- opposite, or whorled; flat; somewhat leathery; petiolate; without marked odour; simple. Lamina entire; linear to lanceolate (glabrous, acute or sub-acute); pinnately veined; attenuate to the base. Leaves exstipulate. Lamina margins obtusely serrate to dentate (the teeth gland-tipped). Leaf development not ‘graminaceous’.

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

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence units cymose. Inflorescences few-flowered, axillary. Flowers medium-sized; regular; 5 merous; tetracyclic. Free hypanthium present to absent. Hypogynous disk present; of separate members to annular (in the form of a 5-lobed disk alternating with the stamens).

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; shortly gamosepalous; 5- toothed. Calyx lobes markedly longer than the tube. Calyx regular; not persistent (the lobes deciduous); imbricate. Corolla 5; polypetalous (inserted beneath the obscurely 5-lobed perigynous disk); imbricate; regular; white. Petals obovate, shortly clawed; entire.

Androecium 5. Androecial members free of the perianth; all equal; free of one another; 1 whorled. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (the filaments filiform). Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse.

Gynoecium 5 carpelled. Carpels isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 5 locular; sessile. Gynoecium stylate. Styles 1 (the style subulate, twisted and 5-furrowed); attenuate from the ovary; apical. Stigmas 1. Placentation axile. Ovules 2 per locule; funicled; horizontal; collateral; non-arillate; anatropous (?).

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (loculicidally 5 valved, the valves extending through the style, ultimately recurved, cohering below, bipartite above). Dispersal unit the seed. Fruit about 4–10 seeded. Seeds endospermic to non-endospermic (i.e., almost exalbuminous). Endosperm oily. Seeds quite large, oblong, compressed, shining. Embryo well differentiated (large). Cotyledons 2. Embryo straight.

Geography, cytology. Antarctic. Temperate. Endemic to New Zealand, North Island.

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

Species 1. Genera 1; Ixerba (I. brexioides).

Economic uses, etc. A valued source of honey.

History of the encoded description. This draft description by LW (2009) lacks information on embryology, anther development, pollen and phytochemistry. As it stands, it shows Ixerba (temperate) differing clearly from Strasburgeriaceae in leaf form, the flowers aggregated into inflorescences, and details of perianth, androecium, gynoecium and fruit.

Illustrations. • Ixerba brexioides: Hook. Ic. Pl. 6 (1843). • Le Maout and Decaisne: Ixerba (with Brexia).

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: 8th June 2026. delta-intkey.com’.

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