| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Rhabdodendraceae (Engl.) Prance

~ Rutaceae p.p.

Habit and leaf form. Tall, fastigiate or subpyramidal shrubs. Leaves alternate; leathery; gland-dotted; simple. Lamina entire. Leaves stipulate, or exstipulate. Stipules if present, caducous.

Leaf anatomy. Stomata present; anomocytic. Hairs present. Complex hairs present; peltate (short-stalked, with siliceous inclusions). Lamina with secretory cavities (also with scattered fatty bodies). Secretory cavities containing resin; lysigenous. The mesophyll with sclerenchymatous idioblasts (traversed by fibre-like, simple or branched sclereids representing prolongations from the vein ends, and many of the mesophyll cells with silicified walls).

Axial (stem, wood) anatomy. Nodes multilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring (R. macrophyllum only), or anomalous (the others). The anomalous secondary thickening via concentric cambia.

The vessel end-walls simple. The axial xylem with tracheids; with fibre tracheids. The parenchyma largely apotracheal, or paratracheal (then very scanty-diffuse). The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones, or not stratified (?). ‘Included’ phloem present.

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

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes. The ultimate inflorescence units cymose, or racemose. Inflorescences axillary (or supra-axillary); racemes, or racemelike cymes with terminal flowers. Flowers regular; cyclic; polycyclic (by virtue of the androecium). Free hypanthium present (short, the flowers slightly perigynous). Hypogynous disk absent.

Perianth with distinct calyx and corolla; 10 (or the calyx more or less entire); 2 whorled. Calyx basically 5 (but the lobes short or obscure); 1 whorled; gamosepalous; five lobulate to blunt-lobed, or entire; regular; imbricate (when lobed), or open in bud. Corolla 5 (sepal-like); 1 whorled; polypetalous (the petals glandular-punctate); imbricate and valvate (slightly imbricate below and valvate above, or cochlear); regular; deciduous (caducous).

Androecium 25–50. Androecial members when the stamens not developing more or less simultaneously, weakly maturing centripetally; free of the perianth; free of one another; more or less 3 whorled. Androecium exclusively of fertile stamens. Stamens 25–50; polystemonous; erect in bud; shortly filantherous (the filaments flattened, persistent). Anthers basifixed (elongated, apically emarginate, caducous); non-versatile; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; colporate; 3-celled.

Gynoecium 1 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium monomerous; of one carpel; superior. Carpel stylate; with a gynobasic style (the style thick, virtually basal, externally stigmatic for half to all of its length); 1(–2) ovuled (the second, if present, abortive). Placentation basal. Ovules epitropous; orthotropous, or hemianatropous; unitegmic.

Fruit scarcely fleshy, or non-fleshy. The fruiting carpel indehiscent; drupaceous (globular, borne on the woody pedicel and shortly stipitate within the cupular hypanthium, the exocarp thin and eventually crustaceous, the endocarp slightly woody). Fruit 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (thick, fleshy). Embryo bent (the radicle bent inwards towards the hilum).

Physiology, phytochemistry. Cyanogenic. Betalains absent. Sieve-tube plastids P-type; type I (b).

Geography, cytology. Neotropical. Tropical. North Brazil, Guianas. X = 10.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae (? — reassigned on the basis of rbcL sequencing, Chase et al. 1993); near Caryophyllales (?). Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales.

Species 4. Genera 1; only genus, Rhabdodendron.

General remarks. The anatomical components of this description are inadequate, but records of anomalous secondary thickening and libriform fibres seem out of place in Rutaceae.

Illustrations. • Rhabdodendron macrophyllum: Nat. Pflanzenfam. III (1915).

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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