| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Stackhousiaceae R. Br.

~ Celastraceae.

Habit and leaf form. Herbs. ‘Normal’ plants, or switch-plants. Leaves well developed, or much reduced. Plants succulent, or non-succulent. Annual, or perennial; the perennials rhizomatous. Mesophytic, or xerophytic. Leaves alternate; spiral; ‘herbaceous’, or leathery, or fleshy, or membranous; petiolate to sessile; non-sheathing; simple; epulvinate. Lamina entire; linear, or lanceolate, or oblanceolate; one-veined, or pinnately veined. Leaves inconspicuously stipulate. Stipules interpetiolar; scaly (or terete); caducous (usually?), or persistent. Lamina margins entire.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Stomata present; anomocytic. Hairs present; eglandular; unicellular. Complex hairs absent. Adaxial hypodermis usually present. The mesophyll without crystals.

Axial (stem, wood) anatomy. Primary vascular tissues in a cylinder, without separate bundles (? - since rays are said to be absent); collateral. Secondary thickening developing from a conventional cambial ring (?). Primary medullary rays reported absent.

The vessel end-walls simple. The axial xylem with fibre tracheids.

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

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, or in racemes, or in umbels. The ultimate inflorescence units cymose, or racemose. Inflorescences racemes or cymes, rarely umbellate. Flowers bracteate; bracteolate (usually, with two bracteoles), or ebracteolate; fragrant (mostly?), or odourless; regular to somewhat irregular. The floral irregularity involving the androecium. Flowers 5 merous; cyclic; tetracyclic. Free hypanthium present. Hypogynous disk present (lining the floral tube).

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous (on the hypanthium), or gamosepalous (towards the base above the hypanthium); regular, or unequal but not bilabiate; imbricate. Corolla 5; 1 whorled; polypetalous, or gamopetalous; imbricate; unequal but not bilabiate, or regular; white, or yellow, or pink, or purple. Petals clawed (the claws free, even when gamopetalous above).

Androecium 5. Androecial members free of the perianth; markedly unequal (usually three long and two short), or all equal (Macgregoria); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers dehiscing via longitudinal slits; tetrasporangiate; appendaged (Macgregoria), or unappendaged. The anther appendages apical. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate; 3-celled.

Gynoecium (2–)3(–5) carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil (2–)3(–5) celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary (2–)3(–5) locular. Gynoecium stylate. Styles 1, or 2–5; free, or partially joined; attenuate from the ovary, or from a depression at the top of the ovary; apical. Stigmas 2–5. Placentation axile to basal. Ovules 1 per locule; ascending; apotropous; with ventral raphe; anatropous; bitegmic; tenuinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3 (sometimes multinucleate); proliferating (to form 10–15 cells), or not proliferating. Synergids pear-shaped. Hypostase present. Endosperm formation nuclear. Embryogeny asterad.

Fruit non-fleshy; a schizocarp. Mericarps (2–)3(–5); comprising nutlets, or samaroid. Fruit 2–5 seeded. Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present. Aluminium accumulation not found.

Geography, cytology. Temperate to tropical. Malaysia, Australia, New Zealand. X = 9, 10, 15.

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

Species 27. Genera 3; Macgregoria, Stackhousia, Tripterococcus.

General remarks. Apart from characters depending on limited sampling (enbryology, anther wall development) and the restricted geographical distribution, the compiled data show Stackhousiaceae differing from Celastraceae sensu stricto (q.v.) only in the herbaceous habit and schizocarpic fruits.

Illustrations. • Le Maout and Decaisne: Stackhousia, Tripterococcus. • Macgregoria racemigera: Hook. Ic. Pl. 13 (1877–79). • Stackhousia monogyna, habit and inflorescence. • Stackhousia monogyna: Bot. Reg. 1917 (1836). Stackhousia monogyna. 1, longitudinally opened corolla. 2, longitudinally opened flower with corolla and gynoecium removed, showing alternately long-and-short stamens and the hypogynous disk. 3, gynoecium.

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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